Originally posted by Big Chaze
You grab a bucket.
Fill it with warm water, (you can add a little soap if you want).
Grab some sand paper, (I use 400 grit when doing my bumper).
Dip the sand paper in the bucket of water, and begin to sand your car.
This is called wetsanding.
I heard it's best if you let the sandpaper soak for at least 30 min.