paging Nordie....

its not hard to do, just takes a lot of grunt work.  there is no "easy way" or "magical polish" just a lot of elbow grease.  a machine helps.  an angle grinder with a buffing wheel, a bench grinder with a buffing wheel and rouge from harbor freight.  the green stuff seems to work really good.  big scratches need to be removed via sand paper, like 800, then 1000, then higher, then polish.

What he said. I polished my whole jet pump.... alot of work. Search on google for buffing tips there are alot out there. The trick is just to go through the stages. I usually start with 80 grit on a DA if it's cast, then 220, 320, 400, 600 etc.... but usually I can start buffing after 400grit with the right compound. Then I have 4 buffer wheels, each with their own rouge color. Start off with a rouge that cuts material, then to the next to make it shinier, then go to the polishing wheel. It's alot of messy work, but it's nice to be able to polish anything aluminum when you want.