Pretty much covered. Ammonia, or ammonia based cleaner, and a razor blade. If you go to a tint shop, you may be able to buy a plastic razor blade which can be used on the rear windows without cutting the defrost lines.
For anyone looking to take tint off, spray the tint with ammonia, or a cleaner, and use the moisture to stick a black trash bag to the tint, park it in the sun for 15min, and the adhesive, or most of it should come off with the film as you pull it off.