I'm not familiar with the product you're using, but have had decent results using pre-mixed drywall mud. I use a clean rag, wrapped around a finger or two (depending on the size of the structure) and dipped into the mud. Smear it onto the pre-painted walls, working it into any difficult areas, then allow it to dry - usually a half hour-or-so. This method works best on walls where the doors, windows and other exterior details have not yet been added.Next, using another clean soft rag (dry) and preferably working outdoors, wipe the excess off the faces of the bricks. Shake-out the rag frequently (the main reason for working outdoors). This will give you fairly stark white mortar lines, common on older buildings when they were new, and slightly subdue the colour of the brick.
For an even more subdued look, I apply a wash of PollyScale paint - a small amount of paint, lots of water, and a drop or two of liquid dish detergent to allow it to flow. The colour you choose can dramatically alter the finished appearance, as it also subtly alters the colour of the brick. Apply it generously to the top of the walls using a wide (1/2") brush, and allow it to flow downward of its own accord. Siphon-off the excess as it collects at the bottom, using either the brush or a paper towel. Make as many applications as you wish, but avoid brushing the surface if possible - you don't want to remove the mortar.
This building, an old Revell kit, was airbrushed with Floquil Reefer Orange, then treated in the manner described, with several grey and brown washes added:
This modified Walthers kit, with less-pronounced brick detail, got the same treatment, followed by only a light wash of grey:
Varying the brick colour will also change the appearance. I used a colour similar to boxcar red on this one, then applied the "mortar", with no wash added:
Pre-mixed drywall mud can be found at home improvement centres, hardware stores, and builders' supply yards, and is available in many different sized containers. A small tub will go a long way, so don't buy too much. It can be stored for some time after opening, but can eventually become mouldy.
Wayne
Any post with pictures by Dr Wayne is worth a thousand posts of words alone
I have used the premixed drywall mud myself with good results (I think) Here is a picture of a Bachmann Spectrum Hotel that I sprayed with brown primer and used premixed drywall mud for mortar
John R.
The secret is to wrap your finger in the cloth and use a fine weave cloth like pieces of a cheap flannel shirt, sometimes you must dampen the cloth with whatever is the solvent for your mortar (water if I remember right with this product).
Thanks for your kind words, EmpireStateJR.
I'd say that the photo of your hotel has exactly the same effect. Very nicely done.