And here's my opinion....
Take the car to a shop, and have them do the rear window. I prefer 3M film, it's guaranteed not to turn purple like cheap tints.
If you want to try tinting yourself, I am all for that. I've done quite a few cars myself. Go for it on the side glass, but honestly, leave the rear glass to a professional. If you mess up the rear tint or it bubbles or fades in a year, there's a good chance you'll destroy the defroster grid trying to get it off.
Let a shop do the rear.
2012 Race Red 5-door SE, 18" Ti wheels, Ti headlights/fog bezels, 20% tint, debadged trunk
2002 Sonic Blue SVT - supercharged (sold)
2008 Vista Blue SE (gone)