[thstone]

Yes, open the cap to the brake fluid reservoir first. Otherwise, the pressure may not allow the fluid to flow back into the reservoir. Keep an eye on the fluid level as you push in the pistons to avoid any brake fluid overflow!

Use a slow yet firm and steady pressure on the piston and it should retract slowly back into the caliper. Be sure to apply even pressure acros the piston and not to just push on one edge. Use a flat, thin piece of wood or metal to provide a wide and even surface to push in the piston evenly.

Don't open the bleeder valve on the caliper. Not needed if you follow the above advice.