The method that is used here on these boats is as follows:
Nail on the planks - driving the nail
head 1/4 below
wood surface.
Sand the
wood so it is even. Twist the cotton and push it into the gaps between the planks. Then drive the cotton in with the caulking tool.
Then
paint with primer. Then use "machun" - a type of putty/filler that hardens off. Fill the nail
head recesses as well. Sand it all down to a nice finish. Maybe another coat of primer then the
anti-fouling coat.
How does that sound ?