If there is any significant rust you would be better served to have it blasted. Ask around or look up media blasting or fabrication shops. Otherwise you will strip, then sand out rust, then sand some more. Around here I can get something the size of a bike frame or truck wheel blasted for about $20.

Wear safety glasses if you use stripper. Little flecks of it fly all over even if you are careful when you apply it to areas like dropouts and seatpost clusters. Stuff is nasty. Also the orange "chemical resistant" gloves do not stand up very well.