1st dig out all loose gelcote & clean the area with acetone.
Next get some powered airosil. The airosilwill thinken with the gelcote into a nice past & will also absorb the color.
Once you have you consistence dab the gelcote without harder into the damaged area. Look for color match. If it is off then tint it with the needed color.
Once color matches start the process.
Tape off the area of repair with about 1" of boarder into the good gelcote.
Pack the gelcote into the damaged area.
Next cover the repair with waxed paper. This will smooth out the job and spread it onto the taped area.
Once dry start sanding with 80 grit.
Once you start sanding into the tape & then remove the tape.
Next start wet sanding with 220, 400, and finally 600.
Once done compound out with a machine.
Note once the gelcote dries and you remove the waxed paper if you have air voids aid more gelcote & re cover with the wax paper.
To me, I think I have a problem because if the boat is at my house I love doing repairs to gelcoat. Seems so forgiving and can get a great product from an ugly environment. Larry's post is straight on, I never did the 80 grit bit so spent more time doing a higher grit, again its all about learning here right?
I got some awesome comments on my General Marine when I kept that in great shape. So moving into this awlgrip boat now not real happy. Someday maybe I will get it in my yard to do.
Color matching also wasn't that hard when I had the blue hull nor off white either.
One thing I am curious about now is I would like to get Gelcoat in Sea Foam Green that awlgrip makes, trying to track that down or see how I can get it.
For gash deeper than a 1/4 inch you may want to fill, with Formula 27 filler, then gel coat on top of that.
You can build up an area with several coats of gel coat if the nic is not too deep as well. But, that chunk looks like some filler will help as gel coat is very thin and smooth and not made to fill.
Blue tape off the area of the scar so that you don't "over do" the area beyond the skin scar with gel coat or sanding. Se El Mar's video by Tap Plastics and go for, it's gel coat you can always, reapply and sand off . Do use 200 and 400 grit paper, they make wet sand special paper too. Even if a heavy layer of gel coat applied, just start with 150 grit, then 200, dont scratch more than it is needed by using heavy grit paper.