automotive primer, color and clear finishes from the auto store work well,
you don't have to remove the old paint, just sand it flat and clean the whole frame with a good degreaser and paint prep, usually an acid.
unless you have an oven big enough for you to bake your frame, the paint will chip eventually, especially on the dropouts, top tube etc.
power coating isn't that expensive, and will stand up to alot of abuse,
when you factor the cost of the auto paint, degreaser, sand paper, buffing compound, paint prep, it adds up to somthing not to far from a decent powder coating
my 2 cents