Our RV tech, who built boats for a living in his 'prior' life, told us to take our gel coat repair kit (such as https://www.westmarine.com/buy/west-...-kit--14153282
), mix a bit up and, with a gloved finger, dab it slightly into the hole. Don't try to fill it all the way, just dab a bit on. Let it dry and then repeat the process until it's the same level as the rest of the body. After it's thoroughly dry, use an ultra-fine WET sandpaper on it to knock it down so it's smooth. Then buff out with a buffer and wax it as needed. Maybe someone else has another way, but that's what we're going to do to fix our small ding.