I've used a pressure washer with pretty good results. What worked for me was 3500 psi washer. You can pull a lot of the surface rust off of the frame. Just be careful of soft parts (wires, hoses, fingers, etc.). You can also push out gaskets on small parts like carburetors and valve covers if you are not careful. I use Ironguard equipment enamel from the local implement dealer. It comes in quarts, gallons and spray bombs. You can paint it on bare metal and it comes in several colors.
