i would disconnect the cables at the pedal and see if its free, if so! connect one cable and try it again. when you find the one sticking, remove the pin from that cable at the backing plate on the brake drum and try it again. this the best way to isolate the problem.
That happens alot.... The fix we do is, loosen the 9/16 nut on the bottom of the brake pedal just a half a turn to a full turn. Then spray it with some lubricant and then heat the bushing up with a torch. Not to much but just a little heat will loosen it up, and you will be good to go!