In response to an introductory by Ben Spragg there was a reply. As the topic then drifted I thought it better to move the posts to the "Help Desk" area...
Nice boat - looks like a Reedcraft. Original trailer too, which is a bonus. Mine is similar. They suffer from gelcoat crazing but I sorted mine by using a proper grp primer to fill the cracks and then Sadolin White Woodshield, an expensive water- based highly-pigmented resin paint that I have used for many years on exterior woodwork! Sounds crazy but it has out-performed any oil-based paint I've ever used on grp. Sadolin are interested in this as they have never tried it on grp. All I can say is that it works - and my boat lives in a harbour with salt water and harsh sunlight that destroys marine oil-based paints in two seasons.
Enjoy the boat - they sail really well and cope with rough conditions, providing you reef early.
The gelcoat on mine had thousands of fine cracks with a few wider cracks in places. None of it had flaked off so the surface was still flat. I started by washing the surface with brake cleaner to degrease it using thick gloves and lots of clean rags. After a couple of days drying, I then smeared cellulose filler across the whole surface - just a thin smear to fill the cracks. The filler comes in tubes and is designed to fill cracks in automotive paint. I then sanded it with 100 grit silicon carbide paper, cleaned it with panel wipes and painted with two coats of grp primer, sanding back between each coat. This all sounds like a chore but doesn't take that long with the right gear and temperature (summer!).
I then gave it two coats of Sadolin White Woodshield - a satin finish. Use this with high quality brushes at lower temperatures (10-15 deg C) to let it flatten properly. The result is a smooth tough finish that has stood the test of time. This is a water-based paint but cures in around 48hrs to a waterproof coat. I use it on all exterior window frames and doors at home - far better than conventional oil-based paints. It lasts for at least 6 years and is very easy to sand back and recoat. The boat still looks great after 2 years cooking in Lyme harbour, even on the parts where I clomp about on deck.
Hope this helps