If you don't want the rust to come back MAKE SURE you remove all of the rust. Then after removing all of the rust clean them off with rubbing alcohol (residual rust dust painted over will rust from the inside). Next, paint sticks best to primer, and primer sticks best to metal (why do you think primer exists?), so primer them before you paint with the correct primer. Next spray a couple of coats of high-temp paint and you're done. They will never rust again. Do everything right the first time or do it wrong many times, it's up to you.