I recently serviced my Gixer front calipers and found my track pump was good enough to pop the pistons out. Just needed to use some old lines or the tubing I would use to bleed the brakes, connect it to the track pump and away you go. Admittedly it's a bit more tricky once one piston comes out and you need to cover the holes inside the chamber, however that's where having small children comes in handy....they can either stick their fingers over the holes, or, pump the pump while you cover the holes yourself. Just be careful the piston doesn't shoot out and er...hit them in the face
(***NSPCC disclaimer...he laughed about it...honest!)