Welll...... Forget wax. Have heard of paint sealants bc I didn't know anything about them untill becoming a member of AG. Do some research on..... Wolf gang deer gloss paint sealant or Detailer's pro series poli coat paint sealant. Just my thoughts. I really don't know much about wax or paint...
After you get the film on the back glass. Go over it with a heat gun. That will make the film shrink and form to the heat strips. If you don't than within a year or so the film will start pulling away from the window at the strips
DP poli coat paint sealant is sweeeeeeet, cheap and last 2 months but that was with high press washes fallowed by pinnacle shampoo hand washed every week then. It finally pooped out. Time to reapply........