1. A gallon will do it, but a gallon and half would be better. 2 gallons is too thick IMO.

2. Rough up the bottom with some sandpaper. Clean off thoroughly with denatured alcohol or acetone. The instructions on the can call for some type of acid, I don't use it though.

3. It sets up quite quickly, so have everything ready to go. I'd let it sit for at least 2 days before floating anything, and I wouldn't float anything that I was going to bang bottom on for even longer.

I always tape plastic around the rest of the hull and will use rubber squeegies to spread it around.