There is a lot of experts browsing this website. Please correct me if I said anything wrong.

(I am not a technical guy at all)
Dirtmap is now build-in in Maya 6.5. You don't need to download or install anything. It is very simply.
I am a bit lazy to explain, see the window captures. You should be able to understand.
P.S. Make sure the Mental Ray plug-in is on.
