For this Instructable I've selected a coin door from an old Defender cocktail cabinet.
Step 1: Step 1: Take It Apart!
Step 2: Step 2: Clean It Up!
Depending on the condition, you may be able to just remove it with a wire wheel and some time. Me? I prefer the chemical approach.
Edit - July 13, 2009: I've since changed my tune. I now use an electrolytic process to remove both rust and the old coating. https://www.instructables.com/id/Refinishing-Metal-Arcade-Game-Parts/
Step 3: Step 3: Strip 'er Down!
In the second picture you can see how the coating is just bubbling off. In this instance, it was making a sound much like Rice Krispies as the air got underneath the coating.
Step 4: Step 4: Paint!
Primer is important! It give the paint something to grab onto. It doesn't have to be heavy, but a light coat will give you a better paint job. Primer is thick, so it also helps to cover up any imperfections or blemishes.
A good paint is important! For years I tried getting away with using the cheap paints, but they just don't do a good job. I personally won't use anything except Rust-Oleum brand paints now, unless there's a product they don't offer for a specific purpose.
Different kinds of doors use different kinds of paint. For example, on a classic Midway style door I like using Rust-Oleum brand "Textured" paint because it's a very close match to the original coating. On over/under style doors, Rust-Oleum brand "Hammered" finish works.
For the door in this Instrucable (really a coin plate, really) I used Textured paint.
Step 5: Step 5: Don't Neglect the Insides!
Step 6: Step 6: Reassemble
That's it in a nutshell. Of course every door is different, and there are things I'd do to one door that I wouldn't do to another. You have to use your best judgment.