For the fronts, just use a simple C-clamp to push them in or vice grips. There's a lip on the underside of the cylinder to position the grips against and squeeze the caliper in. For the rears, I used a big ass screwdriver to screw them in. Make sure you line up the rears pistons though so when the pads go and and you apply the brakes, the piston closes correctly onto the studs on the back of the pads. You will want to eye this, but I believe the piston can be screwed till it reaches a parallel/perindicular postion, like the Red Cross symbol (or like this: "+") and they will fit directly on. Otherwise, you'll wear your rear pads out unevenly and prematurely. There's a little vent on the caliper that will allow you to see inside when the piston is closing. Have a buddy apply pressure to the brake SLOWLY to make sure it closes correctly, otherwise, remove the bolt to the caliper, slide up, remove pad and reposition piston.

Also, make sure you don't let the caliper hang by the brake line. You can do some damage here, so use strong twine or a wire hanger to tie it to your spring.