Surfing School - Repairing - Dings
For a deep puncture, such as a hole, or a broken tip on the nose or tail, cabosil or foam dust filler mixed in resin is used. Prepare the area by sanding and taping like you would with a shatter. Lift the edge of the tape up to ensure the resin doesn't get on the rest of the board. Mix a cold (slow curing) amount of resin in a container before adding the cabosil. Mix just enough so the result is pliable like putty. Use a tongue depressor to mix and apply to fill the hole completely.
When the cabosil starts to set, use a razor blade and sandpaper to trim the excess down to the edge of the hole. A final sanding will smooth the repair edge after the resin has completely cured. Mix a hot coat of finish resin and paint over the hole using a 1" width brush, pulling the tape as it sets. After the resin is completely hard, wet sand with fine grit cloth and buff to finish.