If the vehicle hasn't been driven for a couple years, it is most likely that the calipers are sticking on there mounts and not FLOATING as they were designed to do

If it is a hydraulic issue---the only prudent course to take is to completely redo all the seals/pistons/valves

And since it is a 1992 ----there are a couple areas that the steel line to the rear brakes rust out along the frame----