rear tint

Get a bottle of Simple Green household cleaner.  Saturate the tint on the back window, then cover it with Saran Wrap.  Park the car with the direct sunlight for an hour or 2,  The simple green will penetrate the film and break down the glue.  It will then wipe off of your window leaving all defrost traces in-tact.

sure, as long as its a plastic one. the idea is to wet the tint on the inside and then place the bag or plastic over the simple green and squegee it on. the simple green will keep it stuck on the window. regular soapy water works too. depending on how long you "sweat" the tint, you may have to go back out and peel back the bag and spray some more in there and squegee it again, just keep it nice and wet. the whole process is also easier to do if you have a weed sprayer you can use rather than a spray bottle.

if you try and take a razor blade and glass cleaner to your back window like you would the other windows to strip off the tint, you will ruin the rear window defroster grid and it will no longer work.