Take the brake hose off and put the caliper between 2 pieces of wood in the vise. I just did this the other day and it worked fine.
ERIC

 

Today, I removed the plug pin, pins and brake pads. Now, I need to get a good C-clamp to push in the piston. I almost made a fatal error the c-clamp we have. It is the type of clamp where the flange and the bolt are separate. Well, when I started tightening the bolt, it came through the flange and chipped a part of the the cushion-like material on the piston. It isn't terrible, but there is a small chip.

For those who have been in my situation, what is the problem, and what do I need to do.

With this one, the impact driver saved the day. I could not have continued without it. For anyone who doesn't have an impact driver, Sears sells them for $25.

 

Try sticking a brake pad back in then let the C-clamp push the pad instead of the pistons.
ERIC