I really only use the buss compressor as "glue", not as a volume booster.
I have a preset I made myself, but tend to tweak it based on the content of the mix. Basically, it's the threshold around 9:00 (adjusted so that the needle is never hitting 4db or above on the meter), attack .10, fastest release, and a 4:1 ratio.
A smidge of make-up gain, but that's it. Like I said, I'm using it for the color it imparts, as well as the "punch" factor. I participate in the loudness wars later, after the mix is printed...
Oh, and I try to keep my master fader at around -6 to -4db.