Ok, so only one rear wheel seems to be working with the parking brake (driver's side only). The passenger rear wheel only kinda' works when you pull the parking brake. I've adjusted the parking brake, but it hasn't helped.

So, I pulled the parking brake cable apart at the joint under the middle of the truck. The cable to the passenger rear wheel seemed seized. I worked with it using a lot of WD40 and I got it unstuck, but it still doesn't seem to slide in the larger rubber hose as smooth as it should. I had to pull off the rear drum and shoes and disconnected the cable on the brake shoe, too.

Now, after putting the drum back together I can pull on the cable at the joint under the middle of the truck (using vise-grips). However, when I pull the cable it won't return on its own. I can push the cable back with the vise-grips, but shouldn't it return on its own because of the spring that's attached to the other end of the cable at the brake shoe??

Finally, the brakes on the rear drum could probably stand to be adjusted out a little bit as they're worn and I'm thinking maybe this would help the parking brake engage better. However, I'm still a little confused as to whether or not the parking cable should return on its own when I pull it with the vise-grips.

Make sense??

Any thoughts?

You can't push a rope.
You should replace the bad cable. If you don't you'll end up with brake issues.
And yes the springs in the brakes should return the cable.