Brakes locked on Holiday Rambler

Because of the info above, caging them will not help. If you are not willing to rock it back and forth more aggressively I would chock the wheels, release the brakes, and hit the drums with a large hammer in as many places as you can. If this does not do it then I would take a long chisel and wedge it under metal end of the brake pad at the S cam that applies the brakes with them released. A normal pry bar might just fit and if all else fails a small sharp chisel into the end of the lining at the drum surface will but you will mess up a little of the pad but not enough to hurt the braking.

Your parking brake is on the rear axle only.