Thanks Bullet. Basic color and making logos in illustrator I can do. It's the stuff that takes talent like painting realistic distressed paint, metal, wood, etc. that I have no idea how to do and there does not seem to be any good reference material to help one learn. It's like a big industry secret that is only taught in art schools or something.

It goes beyond just PS as well. For instance I know you can use vertex painting techniques in conjunction with maya and mental ray shader nodes, and applying noise, and fractal patterns one can create maps that can be used as masks in PS or with shader networks to automate and randomize the rust and wear areas on a surface.

One can also generate a map from the ambient occlusion render between two surfaces as rust generally accumulates in the areas of shadow between parts.

Alas, the only tutorials I have seen that use the vertex and ambient occlusion mapping methods was for 3ds max and was beyond my abilities to translate into something I could use in maya.

I can tell you someone, somewhere is missing a big opportunity for training in this area. All you see are grey scale occlusion renders (if you are lucky, screen grabs if not) along with basic modeling tutorials. Occasionally you see some beautiful final fully textured and lighted renders from talented people but god only know how they learned it and they don't share!