How To Apply Texture to uneven Surfaces

http://psd.tutsplus.com/tutorials/photo-effects-tutorials/how-to-apply-textures-to-uneven-surfaces/
Applying texture to a flat surface, or flatly applying a texture across a whole image (as a means to age it or degrade it) is simple stuff. Realistically applying a texture to an uneven surface is much more hands-on (more so than simply overlaying a texture and changing the Blending mode).