i used to work at a auto glass place for a summer job back when i was a teenager, i hated that job LOL i had to remove tint all the time.
anyhow all they really did was use an assload of window cleaner and a razor blade, the window cleaner would help keep it moist and let the razor glide easily. i don't think a heat gun or anything would really help. some tint came off very easily, other products were a nightmare... usually the cheap discolored stuff was a real pain in the ass. if you're lucky you can use the razor to lift up a little bit of tint then pull large sections of it off. if you're not lucky, well you'll be using the razor a lot.
just be very careful when you're doing your rear hatch glass, because there is very small lines that you can cut easily with the razor breaking the circuit, or if you make it too thin won't heat up to defrost your windows as good as new. and the hatch glass is a fortune to replace. you can repair it i think by soldering new lead in place or something if you break the lines, but that's a real pain in the ass as well, so again just be careful.
get yourself one of those blade holders from lowes or home depot or something that hold like a 3" long blade with a nice handle, it will make it go much faster.