Acid!
I'm gonna stick with what I know has worked for me in the past Mother's aluminum polish that I get from the local hardware store. Either I do it by dremel with cotton polishing wheel and rouge compound. I have a larger electric motor and polishing wheel but don't want to use on the trailer...only has one speed and when you loose grip of the part (tends to happen handling smaller pieces) off it goes like a bullet! Often damaging the corners of the piece
