Ahh No Breakes!!

So I am changing the rear disk breaks on my 94 mustang. And When you take off the pads there is that pisston that you need to puss back in. Well I've tried everything to put it back in. I tried to just push it in with a C clamp, I've tried twisting it(not very much..I was burned out after all the other stuff) but I called around and they said to twist it while your pushing it in. My question is how?? There are a couple groves in the face of thew piston but I don't have anything that would fit them and twist at the same time.
Any sugestions will help.

Thanks
TOM

Well I didn't get that tool and still got it back in. All I did was you a pair of pliers and grab the notches and twist it in. Then put the break pads on and then the disk(I think is what its called, the thing that the pads squeese) and finally screwed it back on. I might get one of those tools for next time but I do n't know yet.

Thanks
Tom