Does automotive window tinting tint film affect the rear window or back glass defroster?

It will not negatively affect the defroster.  In fact, it will improve its performance by trapping more heat to the glass.

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What solution do you use to install the automotive precut window tinting tint film?

Mix 3ml (3/5 tsp) of the Filmvantage concentrated application solution or baby shampoo to 32oz bottle clean water.

Do I need to shrink the automotive precut window tinting tint film?

If going on a contour glass, the tint still needs to be heat shrink with a heat gun on the outside glass prior installing it on the inside.