Devcon 2 ton would definatly be best and the strongest, you can use clear nail polish but it will eventually yellow. If the ding is not very deep just a couple of coats with a brush will work. Be more worried about sealing the the bait than filling it in. The epoxy will be dense compared to the balsa wood and compleatly filling in a deep ding will throw the action of the bait off. The fish wont notice the ding anyhow.