My helmet, purchased from Europe, has now been stripped of paint and rust, and today I primed it with Rust-Oleum Rust Transformer. This stuff is supposed to neutralize any remaining rust by chemically changing it to something inert, over which you can safely apply paint.
I found a place where I could spray paint the helmet -- no, not the kitchen table, the backyard garden! I put it on a flat, aluminum paint pan and started spraying. Of course, my first efforts created drips, so I had to use steel wool to wear those drips away, then respray. If you aren't used to spray painting, you must learn patience, one thin coat at a time, to avoid drips. After drying, I lightly rubbed with fine grade steel wool to smooth the surface.
Tomorrow it will be time to apply the olive green paint (some call it field gray). The primer coat gave me some valuable practice today. Once I finish that, I can apply military decals and the inner liner and chin strap. When Halloween arrives, I can wear the helmet and go to the party as a Democrat. Har har!