I have not painted appliances, but I have painted a couple of metal cabinets, a mail, box, a wheel barrow, and other outdoor items.
One thing that I swear by is a product called “Rust converter.” You sand off the loose rust and then apply the converter. It literally changes any remaining rust to a more stable substance. Then you just paint over it. I have had more luck with rehabilitating rusty objects since discovering this stuff.