With limited budget you can try chalks, any sort, and Dullcote.
First try:
Dullcote (it will take the glossy look and made the surface better for chalk)
chalk powder from the sand paper, appllied with a brush. When you're satisfied, again
Dullcote (this will seal the chalk, until now, you can remove the chalk)
You can see my way at weathering
Wolfgang
Pueblo & Salt Lake RR
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The Conrail SD45 on the right. It is my first weathered diesel. I have done some more to it since I took the pictures so I need to update them. But for now, you can look at these.
F7, modern day, was trying to make it look like it hadn't been washed for a few years.
A few years? More like a few decades!
Keep practicing!
Here is my contrabution to your question. I Havn't started weathering any locos myself yet but I plan on it. I would if possible do some reserch on it go out take pictures if possible to see the real thing to get a basic idea of what it looks like. If possible try to get shots of the actuall type of loco you will be weathering. Try practising on something less expensive like rolling stock first untill you get the hang of it.
Here are a couple of shots from one of the local yards where I live. I hope it helps a bit
Here's an F unit that needs a wash.
Dr. Frankendiesel aka Scott Running BearSpace Mouse for president!15 year veteran fire fighterCollector of Apple //e'sRunning Bear EnterprisesHistory Channel Club life member.beatus homo qui invenit sapientiam