If the drums aren't scored badly or out of round I wouldn't have them turned. Just have them checked to make sure they're in tolerance and then scuff them with some sandpaper. Don't worry about sandblasting the studs. It won't hurt them. Like Metal Man says,why Por-15 if you sandblast. Just clean and paint.Rust-O-Leum would work fine on a budget with the clean drums.
Can't help with the rivets,maybe the shop where you took the axle can help.
