Adding water to the foil is probably to activate some adhesive. Then water should be spread thin on the foil, before applied to the camera. If that can be achieved, I suppose there's not enough excess water to penetrate the camera.
Once I had to apply some large, self-adhesive vinyl signs to a sheet of plastic. I ruined three with bubbles and creases before I asked the sign manufacturer (slow developer) what to do. He advised a light application of slightly soapy water to the base and then apply the sign. I was thoroughly sceptical but all bubbles and creases were easy to remove, which I was expecting, and the sign became firmly adhered after 24 hours, which I was not.
I would think that it is suggested here for the same reason but I would also think that, PJ's and other "busy" people apart, it should be much easier to apply the film without defects to such a small area.
mike
