I seem to be quite good at making textures. Especially old beat up textures, weathered and stained. The basic way I do this is that I have a huge texture collection for grunge, painted, dirty whatever I need. I use these photo as new layers above the texture I want to paint. I then apply these in various ways using the layer apply tools. Sometimes multiply works best. Sometimes overly. Or changing the texture layer to grayscale and applying it in one of several ways. It takes experimentation, and fiddling with the opacity. I usually know just how to apply the layers, but that's from several years experience and the fact that I make LOTS of textures. Most of the time I feel the need to make completely new textures for any scene I do in Max. I have several gigs of maps in my library, and at least a gig of photos waiting to be made into maps in my photo files.

Talent is God's gift to you. Using it is your gift to God.