To recap:
Sand the item to a true shape, fill the holes and bubbles with modeling putty, wash the item, dry it with a lint-free cloth, handle only with cotton or rubber gloves on. I'm serious. I use the disposable ones from the hardware store. Cheap!
Then prime the sucker with a cheap spray grey primer. Let it dry for 48 hours, really, then paint it with your colors in any kind of paint you want.
B-)
PS: Dixie Diner is one sorry casting full of bubbles if I remember right. Be sure you fill those voids with Squadron putty and let it dry for 24 hours before you sand etc.