Eastwood carries lead supplies,,tools, etc. if you go over to the HAMB, and run a search, you'll get more info and opinions than you ever wanted. When you find the answer, post it back. I need to know for my bird one of these days.
Buy a can of metal prep, read the small print. Use rubber gloves. Put it on, let it sit, but no long enough for it to dry completely. Put more on, wash it off and dry. Do only a big enough spot each time so nothing dries until you dry it. Bare metal will turn a color. This is the last thing to do before you spray epoxy primer. Don't touch it, and don't let it get dusty.
If you need to remove flux residue from lead you can wash with 50 50 mix of alcohol and ammonia. Or backing soda and water. I prefer alcohol and ammonia , less chance of rust.