For future reference, you can have your frame stripped of all rust and paint at a facility that your nearest auto parts store can direct you to. I don't know the proper name for these facilities, but there are buisnesses that do commercial acid baths for metal, which will strip it down like nothing else, leaving no damage to the frame. As far as repainting it, I would suggest car paint. Thats what I did to my 1940's columbia.
Another good option is a product for firearms called "Duracoat" Its an extremely durable and waterproof do it yourself finish that gun owners apply to guns so that they can subject them to harsh conditions without fear of rusting. This is a permanent finish that will last for decades. Its available in dozens of colors. Any big gun store will have it.