I prefer the helper-at-pedal method. I don't worry about the MC piston going into a rusty-cruddy region since better that happen in the garage than on a steep road. Since I switched to DOT 5 (silicone), I have no rust worries. I once couldn't get any flow from a caliper on my 1982 Aries (1st time brake bleeding). The helper pushed as hard as they could w/ 2 feet and a slug of rust junk blew out. I'm guessing the PO never bled the brakes in 8 years (in humid GA), which shows what can happen if you don't.

__________________
1984 & 1985 CA 300D's
1964 & 65 Mopar's - Valiant, Dart, Newport
1996 & 2002 Chrysler minivans