When you get the paint off, wash it thoroughly with either denatured alcohol or acetone in a well-ventilated area. This will get rid of any dirt and grease and also clean up any traces of the stripper that you used. Then, in order to prevent oxidation, treat the bare metal with a phosphoric etcher. There are several different varieties of this stuff around. If you use one that leaves some sticky gunk, this needs to be cleaned off with alcohol or acetone shortly before painting. Ask your painter what to use for the phosphoric acid etcher -- one popular brand is Metal Prep. It has some detergent in it so it will help clean off any grease or dirt. Once the surface is prepped, try not to touch the metal with your bare hands.