Subject: Re: Brake cylinder pistons seized; how to free?
Laurence;
I once dealt with a stuck caliper piston by removing the caliper from its mounting, then pumping the brake pedal until the piston was pushed out of the cylinder. I think something similar would work for you if you removed the drum and shoes from one wheel at a time, then pumped enough to get the piston moving. This assumes your master cylinder is still operational!
Alec