really, just like getting a car stuck in a pothole to climb out of the pothole by rocking it back and forth, this is your best bet.
you CAN try taking the wheel off, and pounding on the drum with a good sized sledge hammer a bit, you may get enough vibration where the shoe is stuck.
put both wheels on the floor and give it a go, maybe a pair of 2x4 in front and behind the good side, to keep the one good side from moving too easy...
you can also see part of the park brake cable in the handle to see if it is moving like expected.
heat would mean that you are going to replace the drum. so you might as well use the cutting torch as the rosebud.