i like the white letters on my BFG's. The letters (I think) look cool when they're clean and the tire is nice and clean too. I use Murphy's Oil Soap and a brush to clean my wheels. It makes the white and the black really clean.
Zach, though its a bit more work, you can always take the wheel off the truck and do it while its flat on the ground. That way you don't run the risk of having it drop down onto the rim. Just keep a hose nearby incase you have anything drop on the rim.
i tried that too, maybe the bleech white is old? idk but it destroys the wheels.