The Locomotive painting Process?

[SeeYou190]

hbgatsf

Maybe that has something to do with which paint.  I have bottles of Floquil that were thinned and returned to the bottles 20 years ago.  I can still use them.

I have some bottles of Model Master paint that I thinned the entire bottle and then returned the unused portion to the bottle, and this has been fine.

My biggest problems were with returning a thinned amount of Scalecoat II into a bottle of the same colour, unthinned.

-Kevin

[doctorwayne]

I'm surprised that I'd not seen this thread sooner.

You've already received some good suggestions, but I'll throw in my two cents worth anyways.

When I first bought an airbrush, a Paasche dual action, I followed the instructions in the accompanying literature, which suggested that a good exercise to learn control of the paint was to try to create the smallest dots of paint possible.  I practiced this on some flattened cardboard boxes from the supermarket.  Once I learned how to make very small dots, the next suggestion was to place them in a pattern (you could draw it out in-pencil if necessary)...I opted for a simple grid.

This exercise was to teach control of the airbrush, and the object of it was to create lines as thin and straight as possible, as if they had been done with a pencil and straightedge.

I made several tries before getting one with which I was satisfied, and while I proudly kept it for years, it's long gone.  The lines did look like they'd been done with a ruling pen and straightedge, and the dots were so small that they were almost covered by the thin lines.  If I had to try repeating that today, I'd definitely be embarrassed.

The only rattle can I've ever used that impressed me at all was Tamiya's grey primer - it offers great coverage and airbrush-like application.
While I originally used Floquil's grey primer (now long gone) my current choice is lacquer-based, airbrush-ready Alclad II - great coverage and quick drying, too.

I can't recommend any particular brand of paint, as the ones I liked most have been discontinued.

For clear finishes, my preference is Testor's Dullcote and Glosscote.  Both are lacquer-based, and for airbrushing, lacquer thinner works well for thinning both - I usually use it 50/50, or perhaps just a little less thinner.
You can also mix Dullcote and Glosscote, in varying proportions, to create an infinite number of semi-gloss finishes.

For applying decals (and getting good results) I'll simply paste-in my procedure here...

First, I would suggest that you wash the car (or locomotive, structure, etc.), using warm water and dish detergent, then rinse it thoroughly with water and let it air-dry.

Once it’s dry, airbrush it in an appropriate colour(s), then set it aside to let the paint dry/cure/harden, depending on the type of paint you use.

Once that is done, airbrush the entire areas which will be decalled with Glosscote (or your preferred clear gloss) then let it fully dry until there’s no odour of solvent present on the car.  
Don’t apply the gloss only where the decals will be applied - for rolling stock and locomotives, those areas are usually the sides and ends - cover them completely with the gloss, even if the amount of decal work will be very minimal.  
Allow the clear coat to fully cure/harden - there should be no noticeable odour to it, (this minimises the chance of the setting solutions reacting with the clear coat).

Next, use a sharp blade to cut the needed decals from the sheet, keeping as far away from the lettering as possible.  Once you have all of the required lettering free of the main sheet, use a sharp blade (re-sharpen or replace as necessary) and working on a hard surface (I use a sheet of glass on my work desk for this), to trim away as much of the blank paper from as close as you can maneuver the blade to the lettering, using a straight down chopping motion, rather than slicing it away.  If necessary, do this work under magnification (eyeglasses, Optivisor, or loupe).

The reason for the two-part cutting is that slicing the image, even with a sharp blade, raises the edges along the cut line, and when you apply that decal to the model, the setting solution is often insufficient to make those edges settle completely flat onto the surface.

Using a chopping motion has a couple of advantages, first that it allows you to position the tip of the blade as close as possible to the lettering, and second, that when you bring the blade down to make the cut, the chopping movement pushes the edge of the decal downward, which will allow better and easier setting of the lettering when it is time to apply that solution.



Another tip to decrease the chances that your lettering job will look obvious as decals, is to trim the excess clear film from rounded letters or numerals such as B, C, O, P, 2, 3, 8, 0, etc. which are at the beginning or end of a block of lettering.  
F’rinstance, on a CANADIAN NATIONAL car, I would use a simple diagonal chop to remove the clear film from the top and bottom left side of the “C”, and the clear film from the “L” at the end of NATIONAL - this latter chop could be a simple diagonal from the top to the right edge of the foot, but an L-shaped cut would give even better results.

The same trimming can be applied to dimensional data, too, even if you apply it in the blocks in which it’s printed.  For example....

CAPY        100000
LD LMT     120000
LT WT         49000

....trim the top left corner of the “C”, the top right corner of the last “0” in the top line, and the bottom right corner of the last “0” in the bottom line with a simple diagonal chop.
You will be surprised by how much difference it can make in the finished appearance.


Use distilled water for soaking the decal - it's available in gallon jugs at any supermarket, and not at all expensive.  This eliminates any dissolved minerals which might otherwise be present in tap water, and a gallon will do a lot of decals. 
Do not rush the soaking process for the decal, but allow it to release from the backing paper on its own.  If it's big enough to handle with tweezers (not something small, such as a single digit for dimensional data), dip the released film into water, submerging it completely, then, as you withdraw it from the water, drag the back-side of it over the lip of the container holding the water - this helps to remove any residue left from the backing paper.  Depending on the particular decal, you may want to repeat this a couple of times.  
Smaller decals, like blocks of dimensional data or single numerals, can be simply dipped into the water, then set on your work surface while the water frees them from the backing paper.

Most decals applied using only water can be re-wet and moved an almost infinite number of times.  For very small pieces of decal (a single letter or numeral, or even a period or comma, I place the dry decal near its intended place, then wet it with a drop of water on my fingertip or the end of a knife or tweezers.  It can usually be slid off the backing paper easily, then maneuvered into place.

Use references on the model (rivet lines, panel lines, doors, ladders, and other details) as guides to position the lettering correctly and level.  Where those details aren't available, I like to cut strips of masking tape as guidelines, and when lettering with individual letters or numerals, often use a pencil to denote, on the tape, the beginning and end of each word, so that the spacing is correct.
  
Likewise, individual letter spacing is not usually uniform, but rather depends on the particular letters and their sequence within the words.  Google "kerning" for more info.

Once the decals have been applied on the gloss surface and have been blotted using a clean cloth, I use a small brush to apply a fairly weak setting solution around the perimeter of each individual pieces of decal, and also on the decals’s surface - Microscale’s Microset works well for this step.  Let the decals dry fully - it usually takes 10 or 15 minutes at most.
Next, I use the brush-in-cap from the Solvaset bottle to apply this stronger decal setting solution, in the same manner as the previous operation.  I let this dry completely (a couple hours at least, although I often leave them overnight) then use a clean cloth over my fingertip, dipped in the distilled water to wet it, then gently rub the wet cloth over each piece of the applied and set decals - this should remove any marks left by the action of the Solvaset.  Use a dry portion of the same cloth to remove any remaining water from the model’s surface.
After the decals have been cleaned and have fully-dried,  I overspray them with another coat of clear gloss.  This step may seem unnecessary, but the gloss of the decal seldom matches exactly the gloss of the surface on which it has been applied.  This overspray ensures that the entire surface has a uniform finish.

If you're using an airbrush for applying the clear finish, it will dry (to-the-touch, at least) very rapidly, and you can then apply the flat (or semi-gloss, if you're modelling a fairly new car) almost immediately.  After this step, the decal work is completed, and the car set aside, usually at least overnight or for a day-or-so to let the clear coats fully harden.

  
Airbrushing gives you the option of mixing that final clear coat to whatever sheen or flatness you wish for that particular model.

The car can then be weathered as you wish, but unless you're weathering using oils or chalk, I'd recommend no flat overspray over the weathering, as it usually makes the weathering effects too uniform.
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Not a lot has been said about precautions using paints and cleaners, but for cleaners, nitrile or rubber gloves are a good idea if the material is caustic or harmful to skin. 
An example of the latter would be methyl hydrate, a type of alcohol which is a very effective paint remover for some types of paint.  However, it is readily absorbed through the skin, causing damage to some internal organs.

For airbrushing, I always wear a two-stage Cartridge-type filter mask, which prevents inhalation of sprayed paint particles and also blocks harmful vapours from paint and thinners.

My paint shop is located in my detached garage, and the homemade spraybooth is fitted with an exhaust fan and replaceable filters.

About all I can add is that if you're painting steam locomotives, look on-line for colour photos of real ones...very few of them, maybe none, are just "black".

I use black, pretty-well on its own, for the cab and sides of the tender.  For the boiler, and front of the smokebox, the black includes some white and/or grey, and is also used on the deck of the tender. 
The frame and running gear utilises the same paint with a little more grey and/or white, and usually some brown too.

For non-lagged smokeboxes and fireboxes, that latter mixture gets a healthy shot of red.

If the smokebox and/or firebox is lagged, I prefer a coat of Floquil's Graphite, but I'm pretty sure that there should be a more current supplier of that colour.

One the locomotive is painted, it's time to clear-coat some of it.  I do the cab and tender sides with a fairly glossy clear, then a not-too-glossy coat on the boiler and smokebox front (and usually the pilot, too).

The running gear and tender deck get a fairly flat application of clear, while the smokebox and firebox get none.

After that, you can weather the loco and tender to whatever degree you wish, using your airbrush, paint brushes, and/or weathering powders.
For the latter, I prefer oil-based pastels...simply rub them over some coarse-ish sandpaper, then dump the resultant dust into a suitable container.  Use a cheap brush (or a good one that's seen better days) to apply the powder.  I don't use a fixative for this, as my locomotives are seldom handled. 
Overspaying with a clear flat will protect them from handling, but will also lessen the effect of the powders.

A few locomotives done for friends...

...and a few of my own...

Wayne