Showing how I attempted to repair this surfboard (9' 6" longboard). There was some major damage to the nose, tail and rail sections of the board, along with a bunch of smaller dings and cracks, including some water damage. All areas were sanded down, filled with a epoxy filler resin mix, and fibre glassed to make the board water tight. Epoxy resin is quite different to your standard polyester resin and so no "hot coats" were needed. The only finishing step was a quick spray with lacquer.

Let me know if you have any tips on how to do a better job. If in doubt, take it to a shaper to repair it properly, this board was so cheap that the ding repairs would have cost much more than the board is worth.