Put a rag around one piston and blow it out with air. That will protect your fingers. Reinsert, hold with a clamp and blow the other out. Any caliper stuck so bad that air doesn't work needs more than can be done easily and can be sent to the remanufacturer.

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85SD 240K & stopped counting painted, putting bac together. 84SD 180,000. sold to a neighbor and member here but I forget his handle. The 84 is much improved from when I had it. 85TD beginning to repair to DD status. Lots of stuff to do.