With the axle shaft, backing plate, drums and all removed from the truck. Then holding the whole axle shaft in the air, let it drop, straight down onto the ground, so that all 6 wheel studs make contact at the same time and the momentum of the brake drum will force it downwards and off the brake shoes. Kind of like the picture below, except with the drum end down and probably not that high in the air (start low and work up higher if needed):



http://www.4x4wire.com/toyota/maintenance/rear_axle/wheel_bearing/

I found two things tend to hang up the drum, one is the rust around the hub center making that part larger that the hole in the drum. The other is if there is a ridge on the edge of the drum (from wear), that ridge can catch on the shoes.