I found it takes a bit of practice to find the right amount.
Too little, it sticks quickly and can be hard to reposition.
Too much, it doesn’t stick at all at first and slides around until you’ve sqeegeed the water out for a while.
Get the right balance and you have a few seconds to position it before it starts to stick, then you sqeegee to seal it down.
Also some people recommend adding a drop of baby shampoo to the water, if you do this it’s literally a tiny drop that’s needed.
The edges and corners can be a little hard to get to stay down if they’re wet but just aim your hair dryer there to dry it out a little (a little!) and it’s fine.
That’s another point – have a hair dryer with you! Makes it much much easier, warming it while you’re applying makes it more flexible and easier to smooth down.