Gelcoat repair
Like the previous post correctly said,look here and on the net for the detailed versions.
In the short it's a reasonably basic repair.
You mix the gelcoat up,probably paint it on and sand it smooth.
But.The gelcoat has to have 'wax'(industry term) mixed in or it will stay sticky.Wax is on the moulds etc.when the hull/parts are originally made.So this doesn't happen.
Sanding has to be done about 4 times at different grades of sandpaper."about 120grit all the way down to 2000grit before you buff it.Wet and dry is the choice.
Then there is the problem of making it easier to do.Upsidedown on the trailer is not easy.So you have to lay on the floor or roll the ski.
This stuff is all fiddly to do but it is not hard to do.
Hope this helps