I generally just send each drum all the way to the aux track with compression on it, then raise the aux track fader until I have the desired amount of parallel compression. I generally only do this for drums, but when something else needs a little, I'll just adjust the send amount for that instrument until I like it, since I've already got the aux level the way I want it for drums.
I usually use Voxengo MArquis compressor which has a wet/dry, or I duplicate the track and have one with par comp at 0.05ms atk and one with normal attack (usually works out better so you're not increasing the atk on the par comp'd track).
On drums I do it on individual tracks and a TINY bit on the buses.
If you're using distortion on bass/vocals it can really bring out the grind, otherwise I don't tend to use it.