I've tinted a few cars over the years and got good results with Gila tint. They offer different grades of scratch resistance, so buy the best they have. If not, you'll regret it! Been there, done that.
Some tint shops, also, will sell their tint by the foot. The quality is good, if you can find a shop that will do that.
Back windows are a bear, so read the instructions. I tinted the first few back windows 2-3 times before I got the hang of it.
Hope this helps.