Actually, something interesting happens when you get window perf wet... it becomes brittle and easily tearable. Like on a warm day, or warm glass, the vinyl is very plyable and easy to manipulate. As soon as you cool it down and get it wet, it becomes harder to work with.
However, I learned a trick a long time ago... if you find yourself in a situation where your helper (extra pair of hands) leaves you stranded and you've got 32 sq. ft. of perforated vinyl draped over your head and arms, with the backing already peeled off... (and this is not a laminated install at a business) you can actually use Invisible Glass to aide in the intallation. Not the foaming kind, but the kind in the pump bottle. Nice thing about Invisible Glass is there's no ammonia in it to mess with the adhesive, and it evaporates out of the holes pretty quickly.
But dry is the preferred method of installation of Window Perf... it's actually one of the easiest products to install.