Switch to a disc rear end.
But it sounds like it wasn't prepped right. All the rust should be ground off, so it's best to start with new drums. Also, soak them in solvent, there is always grease on them and the craptastic brake cleaner NJ forces us to buy is non chlorinated which sucks and couldn't take grease off anything.
I've never had a problem with duplicolor's caliper paint, I did my rear calipers recently and they look great. My cars are 3 years old and still good, beside being dirty.