Your rear backing plates may have grooves in them that keep the shoes from adjusting all the way out (It pulls them so the shoe is twisted and only part of the shoe makes contact during adjustment, locking the drum, so you think they are all the way out.) OOOH! Another flash of brilliance! I pulled the old Ebrake cables out of mine (They were seized solid) and readjusted them and they worked fine after that. The cable acted like a spring, allowing the shoes to no retract all the way (and gave my brakes a mushy feeling too, like the springs on a trampoline) The first couple pumps in the morning push the cylinders out to contact the shoes (they retract overnight). Make sure your cables slide in and out easy. If you've done all this and they're still mushy, then you have air trapped in the master cylinder or the lines somewhere. (I've had to rebleed some cars 5 times to get all the air out, and air trapped in a new master cylinder can't come out on it's own, because the ports the fluid comes out of are below the top of the cylinder, like an air bubble trapped near the roof of a car that goes in water) Power bleeding is the best cure.