Easy fix with the solar Rez you already have.
1. Make sure area is completely dry.
2. Remove any loose fiberglass with 80-100 grit sand paper and lightly sand around the area where the resin will be applied.
3. Wipe the area with an alcohol swab and let it dry.
4. While in a shaded area, apply a small
amount of solar-Rez over the ding.
5. Firmly cover the ding with a piece of plastic grocery bag cut prior that covers the entire ding.
If you do this correctly, the resin will be flush with board so there will be very minimal sanding if any at all. Think of the plastic as a piece of transparent skin being stretched over the ding.
6. Once the plastic is in place, carefully take the board out in the sun for a minute or so. You can use tape to keep the plastic in place, but it's not necessary if you just hold the plastic in place firmly with your hand.
7. Take the plastic off and that's it. Whole process takes less than 10 minutes.
I would not use a lot of resin as suggested earlier. The worst part of fixing a ding is sanding it. Just use enough to cover the ding(it's less than you think). The most sanding you should have to do is very light sanding with fine paper. If you keep wrinkles out of the plastic, you may not have to sand at all.