i just wet sanded my whole back bumper with 600 grit paper, then used a buffer with compound (turtle wax liquid compound #7 )
just the top right side is buffed.
the whole thing buffed and waxed.
side shot.
i had repainted the bumper last fall, and cleared it, but it got to cold to wet sand and buff it till a few weeks ago.
yes this is a rattle can paint job, duplicolor gm black metallic. and clear.
if you dont have a buffer you will have to really lean on the towel with the compound hard and fast to clean it up, it can be done, its just a lot of work by hand.