Using the various blending modes Photoshop offers you can add a level of richness and authenticity to your texture. The appearance of rust, mold, cracks, a wood grain, and virtually anything you can think of can be made to look like it is part of the overall texture. Overlays are powerful and they should be used carefully or they can override the base texture. Here is a guide to best use them in your work.
This tutorial is derived from my latest book "3D Game Textures: Create Professional Game Art Using Photoshop, Second ed." In it I discuss the latest game technology; shaders, node based materials - you know all the stuff Poser has in it. I notice that the powerful Poser material system seems to scare some away or people don't realize it's there. This tutorial may help warm you up to the awesome power of the Poser material system.