Haha well its pretty darn easy. I'm used to it by now. My sister, however, had something to say when she attempted to back up my car at night! Lol.
Anywho, honestly Richy... the place I got it at, we had 3 cars done at the same time, so they gave us a discount. If you can gather a couple of people who are willing to get tint done also, tinting places might offer you a discount!
With percentages, I dont think they actually do it by percentages. The place I had it done at had four different types: light, medium, dark, and limo I think. So I had dark done to the front and limo for the three in the back.
Any other questions, let us know.