If you don't have enough paint to dip them in or are using a spray can, what I did to paint my restored latches was to cut a small piece of thin wood and put it on the top of the barrel and the underside of the top part when the top is all the way up. This way you can paint most of the top handle shaft that goes inside the barrel. I agree that dipping the latches coats every thing and is probably the best way to do it.
Rusty Nelson