Sealer - Good luck with that. IIRC, the Kirkhams have tried everything to no avail. But polished aluminum holds up for a long time, if not exposed to the elements.
Cleaning Polished Stripes - I'd try the most fine polish that I think is available and that's Nuvite S. If that doesn't work, then I'd try a Mother's Billet Aluminum polish. After that, then I'd move down to more coarse polish in the Nuvite line. They have several levels:
Nuvite Chemical Compounds Corporation - Metal Polish NuShine II System