In my video tutorial series on Render Layers and Material Overides, in the 2nd video, I go over using passes in production.
In that video I show how to apply/tweak the Ambient Occlusion pass by Multiplying that pass over everything.
NORMALY in the post world, this is a NO-NO, but to make the video tutorial more digestible for all involved, I took that shortcut rather than explaining WHY that is generaly a no-no as that would cover a whole tutorial in and of itself, hehe.
SO, our friendly neighborhood MentalRay guru ZAP has released an enjoyable explanation as to WHY and HOW to CORRECTLY utilize the Ambient Occlusion pass from Mental Ray
Israel "Izzy" Long
Motion and Title Design for Broadcast-Film-DS