First make sure the pedal is coming up, if not, pull the handle and lift the pedal by hand.
Second, rather than kill yourself with removing the drums, I suggest the following.
Under the truck you will see where the cables (near the rear of the truck on both sides) go into the cable housing then into the drums.
Get some vice grips and clamp the bare cable about 1/2 inch in front of where it goes into the housing.
Then, take a hammer and tap the vise grips in the direction of the rear of the truck. This will PUSH the cable into the housing (which is probably where it is stuck) and allow the pads to relax. You may have to undo and and re-grab the cable a few times as the cable moves in. If you grab out like 2 inches and try often the cable will just bend, so do the 1/2 inch or so at a time.
Then either lube the hell out of them or replace the rear cable assemblies.