I bought a giant container of bio-degreaser and put it into a spray bottle. A lot of the time I'll do what J does and just wipe it down, add fresh lube, work it in/let it sit, and then wipe it again. If it's particularly nasty I spray the drivetrain with some degreaser first, let it sit for a few minutes and then wipe it down (or spray it down with the hose if I'm doing a full-bike clean) and let it dry off before applying lube.

I also picked up a great thing for when there isn't a hose handy (eg. at races):