I have used the Windex method and it works, however, I like to use the following method it saves weight and there is NO possibility of bubbles!

I make what i refer to as a skin. Starting the light color cut 3/16" larger that pattern (for overlap) and if a wing large enough to work on the edge side. Using a spray bottle with a little detergent wet the glass and place film on the glass, squeegee water out. Then place the next color in place using the same spray mixture and a 3/16" overlap again squeegee water out, then, using your sealing iron set as hot as you can without shrinking the film, seal the edges together. I continue until I have all colors and a complete skin. The skin can then be put on as a single piece of film.

Using this method save weight and prevents bubbles from trapped air between the covering if you just apply trim over the covering base.

This sounds much harder that it is but practice first on some scrap.

The transparent Orange on my "Bingo" was laid on first and then the white. Many think that I painted the white!