I tried the rear window. The tint had delaminated, and now it's just tiny little flakes that come off at a time. Ugh. After an hour of trying, I got frustrated and decided to try a different window. That came off in one piece, quickly.
Back to the rear window...
And so it went. Back and forth. I'd work on the rear window until I got flustered, then switch to a different window, then back to the rear. It was not a fun experience. The old Windex-and-black trash bag didn't work. Steamer didn't work. Heat gun didn't work. That tint was basically a PART of the window at that point. So I moved on to something else - the other door card.