You'll find out on your first one. That works involves skills and patience that many do not have. The precut part ain't spit, and pre-cutting often makes it worse as you have no overlap to be able to be sloppier in location. It's getting the tint on with no wrinkles in it then getting it incredibly smooth after that with zero bubbles, what makes it last. Very hard to locate it perfect at first to have all edges be even, you will be lifting it again and again.
The factory tint work is done on them before the window is mounted in car. That way they can use a big long rubber squeegee to smooth it down all across the glass.
That back glass will show your stuff, it is NOT easy. Why even the $300 jobs fail often in a couple years or less.