Next project includes redecorating some of the rooms in the hotel. New paint for every surface, including the radiators. I have oil-based paints for the trim and was hoping to use that. I know if I ask the paint store, they'll try to sell me a metal-specific paint. Is it necessary? I want to do the job right, but I don't want to end up with more half-used cans of paint than necessary. Also, is it better to paint the radiator when it's cold, or is it ok to paint warm?