Ive had luck with hair dryers, heat gun and rubber hammer. Remove brake lever,shoot PB around the brake cam, heat it let cool,heat again, install lever attempt to move by hand.
Didn't work? heat the surrounding area around the lever, light bumps both ways , work it loose, add more PB until moving freely.
Lever moves freely with no resistance, brake shoes are seized to the drum . Stand the rim up, shoot pb in the hollow at brake shoes ( they are shot anyways), leave the hairdryer on high on the center of the hub, go to the kitchen and make a sandwich, oh , and grab a beer, eat sandwich and watch the wheel ( fire prevention), bump lightly with rubber mallet until it pops loose.
Didn't pop loose ? Remove sprocket , spray ,heat and bump lightly, the shoes are spread open but there is 2 springs pulling them together , that means that the studs that the shoes are attached to have oxidized in the brake ON position, heat the 2 dimples on the brake side , work the lever and lightly bump with rubber hammer. should work. Didn't work? Repeat all of the steps above.