porcelin tub repair?

i need to fix a chip in a procelin tub. i have done fiberglass tubs and need to know if porcelin can be spot fixed as fiberglass can be. do i spray or brush the paint on and does it blend without wet sanding and buffing to get a high gloss finish? i have been in the fiberglass repair business for 20 years and now have a cliet who needs porcelin repair. would like to know the steps and products needed.
any help would be appreciated
thank you

mary petrie
August 2006