Railworks America

Anyone have suggestions for creating rusted panels on freight cars (see attached)?

I've been using layers of various transparency, starting with the tutorial on the 3DT website. I'd post them here, but I'm laid up for a bit and don't have access to them at this time. This is a fairly easy system to tweak.

I think you could add a layer from some real photos. I know you prefer painting, but if you patch your texture with an appropriate sample the result should look very nice.
Do you know textures. com ?
There are several examples:
https://www.textures.com/browse/leaking/580
and
https://www.textures.com/browse/rusted/106800

Registered you have 15 points free every day. Don't forget to mention in your readme that you have used their textures. Otherwise there are no costs.