I suggest pulling the rear drums and cleaning up all of the rear brake components, paying close attention to the self adjusting mechanisms. Lube as needed, re-assemble, and adjust up the brakes manually until you get the slightest drag.
My parking brake was pretty poor before performing this maintenance. Now it engages with just 3 or 4 clicks. The front brakes are so good, I hardly noticed that the rears needed adjustment.
And you live in PA. Just like in WI, your vehicles are subject to "iron oxide errors".
ps- after rereading your original post, it sounds more like an issue with the scissors spring, which pulls the brake lever back against the switch in the dash. This spring is located in the pivot assembly under the driver side of the cab as shown below:
I removed the pivot bolt and added a bushing between the spring and the pivot bolt to keep the spring and bolt concentric.
Between the bushing and the rear brake adjustment, it works great. Hope yours turns out well.