Tom, like you, I am impressed with Aquaguard. I have used it for about three seasons and have used the left over paint without any negative effects. It isn't as ablative as some ( I wish it were), but comes off easily and, if you place a putty knife just right, it peels off--or at least some of it. I don't know what they do, but it used to take me two gallons of paint, but with Aquagard, I can paint the bottom (30 feet water line) with about a gallon and a half!!!! Two coats, too. So, yes, in my experience, you can feel comfortable using the left over paint.

Good Luck

Mike Meier