With 3Ms window films, it is best to read their pdf on the product first. That said, we have always applied them wet using Rapid Tac and a hard squeegee with a felt wrapped edge. If material is masked, then keep the working side dry until you have pushed all the water out - then wet it before removing. If working without masking, spray the working side with RapidTac to help prevent accidental scratching while working the water out. I do not like using a full felt squeegee, like Oshee, as they do not seem to move enough water out from behind the film.
As far as how much application fluid, I usually mist the vinyl and mist the window - not drench either - and that ends up as plenty. you want just enough on the vinyl so that you can get it in position without it fighting you. If the material moves around while you start squeegeeing, then you have too much.
hope that helps.