The easiest way to remove a caliper piston is to pop it out before you unhook it from the hydraulic system. Putting it in a vice and trying to blow compressed air in it is futile. Also, I've seen people damage the piston by blowing it out with compressed air and smashing it against another piece of metal if you are going to do so, place a small block of wood in there to cushion the blow of the impact.
The easiest way to remove a caliper piston is to pop it out before you unhook it from the hydraulic system. Putting it in a vice and trying to blow compressed air in it is futile.
Also, I've seen people damage the piston by blowing it out with compressed air and smashing it against another piece of metal if you are going to do so, place a small block of wood in there to cushion the blow of the impact.