Wire brush it and wash with soap and water. Paint once dry, don't wait.
Paint isn't going to last too long in my opinion.
Depending on color that you want, this works well. Cast iron appearance.
Link is to macs but if you search the product you can get it about anywhere.
https://www.macsautoparts.com/ford_t...E&gclsrc=aw.ds
amazon "speedway"
https://www.amazon.com/Hot-Stuff-Exh...Dressing&psc=1
I've used Calyx and it is a good product. Not sure if the knockoff is as good, or whatever.
Just an option also.