I once taped off all but the painted steel frame of a Raleigh, suspended it from a branch of an old apple tree with nylon rope at seat and stem, and sandblasted it with a cheapo sandblaster and abrasive. It worked well, left no sanding irregularities, and was especially good at welds that would be difficult to sand. It was quick and easy once the taping was done. Wipe with tack cloth and prime before the shiny steel can corrode. Apple tree not required.