The toughest paint i have come across is Duplicolor Engine Enamel. Doesn't need to heat cure and is stupid tough. I have used it for years on car parts and it lasts. Careful with rattle can clear over white as it has a tendency to yellow over time.
As stated the key is prep. You don't need to sand off the old finish if it is in good shape. I would degrease the crap out of it, rough it up with a somewhat fine scotchbrite pad, clean with alcohol, then spray.