Yep. I broke a C-clamp and tore up the caliper once trying to push it in. Autozone carries a tool for turning in the rear calipers. I've not tried it, but I have heard it works better if you bleed off the fluid as you turn it in.
Yeah some needle nosed vise grips will work, and it definitely helps to open the bleeder valve to bleed off some pressure. Also, you can buy a little cube shaped tool that attaches to a socket wrench that will do it. Im sure they are fairly cheap, but the autozone tool kit is nice, it pushes while turning if you feel like shelling out $40 bucks for a few hours until you return it.