How big is the larger area of damage? Less than 1/8" deep you'll be OK. Tape off the area that you want to work on. Use a Dermal tool and clean out the damaged area so there are no loose pieces. Don't go to far. You are only looking for a solid surface for the filler to bond too. Wipe with acetone and use the 3M filler Eric referenced and follow the directions.
3M Marine Premium Filler
After it has been sanded, go over with 3M Acrylic grazing putty. This will fill sanding marks pin holes, etc. It's a 1 part putty that dries in minutes. Sand with 4-600 wet sandpaper.
3M 05095 Acryl-White Putty Tube - 14.5 oz. : Amazon.com : Automotive
Buy some gel coat and match the color to your hull. (Not easy) Once you have it matched, spray on the gel-coat using a Preval sprayer, thinning the gel-coat using styrene or acetone. Wet sand starting with 600 then 800 then 1200 then 1500 wet sandpaper using a block always. Then buff and wax. The results will look brand new.
Preval — The Preval Spray System