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.
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
How does that sound ?