Trying to reset the brake pistons can be quite a hassle, which can leave you feeling frustrated. Mueller-Kueps designed a kit which has reduced the discs needed for resetting to just two.
Included in this kit are two uniquely designed adjustable discs. A two-pin and a three-pin made from extremely durable steel, providea tool that can accommodate almost every brake piston. It works for both left and right threaded pistons.
This tool will do the work for you, simply place the disc against the brake pistons and rotate the basic unit until the pins fit into the bores. Then attach the discs by way of strong magnets nestled in the head of the resetter. The compressed air provides a constant pressure and will not damage the thread in the brake piston.
Link: Mueller-Keups