When you question polishing a bumper I interpret that to mean to take a dull mill finiish on stainless steel to a polished surface. Or a brushed finish to a polished surface.

To start you have to sand the surface to get rid of any imperfections, grain, or surface condition that cannot be polished out. I start with a coarse sandpaper, depending on the depth of the imperfections. I have beaten out a dent in a rear bumper using heavy hammers and as you can imagine it really roughs up the surface.

But I used a coarse paper on a belt sander, something in the 80 range to knock off the high spots. Then I progressively worked my way up though 320, 400, 600, 1000 and finally 1500. It sounds like a lot of work, but if the bumper is new and the surface is in pretty good shape some fine paper and power tools will get it ready for polishing.

I use a 7" grinder with 10 inch cotton buffs stacked to about 1" thick and when the sanding is done I start polishing using a stick of white rouge or polishing compound. There are more agressive compounds but by using the white and working the surface I restored the polish to match the rest of the bumper.

I'm not suggesting this source specifically, but it is one which sells all the stuff you might want.

http://www.swmetal.com/

Here's another.......http://www.caswellplating.com/buffs/...FQFrVAod1Q6nKA

And another........http://www.eastwood.com/buffing.html