From a coating site:

CLEANING

Stains on satin matte finish headers can usually be removed by using hot soapy water or an environmentally safe Orange Cleaner Degreaser and a soft cloth. Never use abrasive cleaners. Two or three cleanings may be required depending on the severity of the stain.

Hi Luster Polished ceramic header finish can be cleaned in the same manner and can be polished with a non-abrasive aluminum polish. (Wax Shop, Mothers, Never Dull)