Go the the local motorcycle dealer and ask for a tube of SimiChrome. It's a paste type polish in a small tube, but you only need a small dab. Use a soft cotton cloth to apply it. The more you rub it, the better it gets (Don't go there...)

It'll turn black, meaning it's actually taking away some of the metal, therby polishing it.

Remove it with a clean cloth and then wash all that black crud off your hands!