I sometimes use one UV channel for procedural max textures like noise, smoke, dent, electricity ect... then render those out and use them when painting textures.
Right now I'm using a "Max Shader" to scatter dust around the objects I'm working on. I blend my defuse with a procedural dust texture, to settle dust on top of everything then bake out my texture. Areas that are not parallel to the Z axis do not receive the dust material (gotta love falloff). Saves me from having to try and figure out where dust would settle. The procedural dust texture uses a separate UV channel, I also render out just the dust with an opacity mask so I can overlay the dust on my texture so I can keep painting without having to re-bake.
I also used this technique to blend snow over complex areas.
I also have a stock set of max materials I keep on hand, they work as a good base to start painting from. They also use a separate UV channel than my final layout. This helmet was textured 100% in max materials in about 30min. It works well as a base to start painting on =)