Parts and procedure for gel coat repair that I did myself are below. We had two repair areas, one on the bow and one half-dollar size on the side of the hull, before pictures attached.
Basic Parts: Gel coat, got it from the manufacture, West Marine stocks other gel coats, may have been close enough Hardener, just bought all purpose hardener from Home Depot Two Preval Sprayer, bought at Home Depot Form Release, Marine stores have small bottle of this stuff, Home Depot didn't have it when I was looking. Blue Masking tape, bought Home Depot Paper or plastic, did not use be will next time to protect more area from over spray Acetone, bought Home Depot Rags Wet sand Sandpaper, I used 1000 and 1200, Next time will start with 800 and work up. Sandpaper, 350 - 400, something like that to rough up application surface Glove and eye protection would be good idea.
Basic Procedure, as I recall it: Choose the proper day. Gel coat with added hardener has a working range, different number of drops of hardener needed for different temperatures. If its windy, pick another day, you don't want to have to wet sand someone else's boat because your spray traveled with the wind.
Prepare surface with 350 - 400 sandpaper, be careful not to create more work by doing to much with this grit paper, less is probably better. Directions for epoxy repair say to feather out the repair on a 12:1 slope. I followed this direction for the gel coat also.
Wipe away dust, use acetone to thoroughly clean.
Mask off area of repair, including feathered area. Use paper or plastic and tape to protect against over spray.
Put in an ounce or two of gel coat into the spray bottle, use acetone as a thinner. I used about 10%, rough estimate, I have been told I should have used 50% acetone, it would have sprayed better. I will try 50% next time. Add appropriate drops of hardener for weather conditions. Mix, shake, whatever works for you to cause the material to be completely mixed.
Spray it on. I started at one side of the repair, squeezed trigger, moved not to slowly to the other side of the repair, then released trigger. Repeat in the other direction. Slowly build up gel coat with each pass. Be careful to not build up to quickly, runs may occur on vertical surface.
Use the other spray bottle to apply the Form Release. As I understand it, gel coat needs vacuum to cure properly and one way of providing it is with form release.
Let it cure for a week. Wash off form release if there is any left. Begin wet sanding as needed with the high number papers. This part will depend on how good of a sprayer you are and if you used the right amount of hardener and thinner.
