Originally Posted by Old Fox

You did find a way though there is a better option without resorting to using the bleed-screw, risking air leakage into the system and loosing some brake fluid. Just open the top lid of the reservoir (mounted next to the front brake lever) and gently...very gently push back the pistons. The fluid needs space to go back and opening the reservoir lid gives it just that. Though this needs a few precautions vis a vis covering the tank and other painted surfaces with a cloth or something to avoid brake fluid spills from damaging it. Also, if you're a trifle quick in pushing back the pistons, a jet of brake fluid will shoot upwards from the reservoir . This is the famed Brahma Press in the reverse you see. Grabbing the pistons with a C-clamp and Slowly screwing it in would do the job pretty well.

One imp note here: Never push the pistons in against the pressure of the hydraulic fluid. Give the fluid some space to expand by either opening the lid of the reservoir or slightly loosening the bleed-screw. Liquids don't compress and using undue force will only end up in damaging the system components (the piston seals in particular).