The windex does not activate the glue on the covering (whatever brand) it allows you to easily move it around and, more imporantly, squegee out all the air. I acutally don't use any water or windex when doing heat-shink over heat-shrink. When doing vinyel (or trim sheet), the windex keeps it from sticking to soon, and allows you to move it around, then squegee out the liquid to make it stick in place.