Any tricks for turning/twisting brake pistons?

I need to turn the piston so that the pad's peg will fit into the notch, so I got the tool from Advance, but it's refusing to twist. Does the piston need to move in/out in order to twist? If so, is there a way to pull/push the piston out some other than with brake fluid pressure?

Thanks!

 

Ok, for what car....front or rear disc brakes....need more info.