This is the best way I have found so far:
Get a beard/mustache trimmer that is electric or battery operated. If will have a much narrower shaving head than that ones people use to cut head hair at home. I;d say they are about 1.5" in width at the most. The best thing to do is get the hair real short using the electric first, and to squat down over a mirror to get a good view. Start at the hole and work your way out. When you are done, give your knees a rest, and take a hot shower. Then towel off and get out a disposable razor and some shaving cream. Squat down again over the mirror, lather up, and wet shave the hole, crack, and and taint. Don't go too far out onto the butt checks or you'll potential break out, and you want to avoid the "landing strip" look if you are like me and have a fair amount of hair in the cheeks themselves. You'll know when you are good and shaves cause you'll see the little bums near your hole and on your taint. It will be REALLY smooth. It's almost impossible not to nick yourself, and if you see a bit of blood, just ignore it and keep going.
That's it. If you do this once a week, you wont have to use the electric first beacase the hair will still be pretty short.
FYI this is NOT a gay thing. You will feel cleaner, crap cleaner, and when you bend over in the locker room with your best work out buddies and they see your crack, it wont be nearly as nasty for them or anyone else to look at.
As for rimming, getting rimmed with a bare/shaved ass it VERY intense. Give it a try.