you need to use a polishing rouge with some buffing wheels either on a drill on a bench grinder....
then to do the finishing polish or to keep them shiny use some autosol...
Having polished bits sucks though, cause you'll be forever polishing them... I did it once, never again powdercoat for everything now...
get them powdercoated, goto Hi-Octane website and check out there chrome colours if you want the polished look, that way you wont have to keep polishing them, you can just wash and dry like you do the rest of the car and they'll keep their shine...