68 barrcuda restore

i am presently restoring a 1968 baraacuda notchback. right now i am working on the brakes. they are disc brakes with four piston calipers. iam having trouble removing the pistons from the calipers. i removed one fairly easily but the other three will not come out using the same method. channel locks were involved and i don't want to damage them if i can help it. any suggestions on how to remove them without damage?