Traditionally folks have cleaned and waxed the boats. General censuses is that a past wax such as Colinite Fleet Wax and 885 is the best wax. Some use Meguiar's Inc M6301 Flagship Premium Marine Wax. There are any number of ways to prep the boat before waxing. Most like to remove as much of the old wax as possible, but others like to leave some base. If you keep the boat up, the every 3 to 4 month wax is not all that difficult. If you get to the point where gelcoat is oxidized, then it may require wet sanding with very fine wet and dry sandpaper--600 to 3000 grit. Also using a cutting paste such as those by 3M--including Finesse it, Currently the product line is Perfect it--3 products, and a series of pads with a variable speed orbital buffer. Harbor Frieight, Porter Cable, or Mikita all make great buffers.
If the gel coat is in good shape, I will use Dawn Soap, Colinite 920 cleaner, and follow with Colinite 885 wax. I happed to have a collection of buffers, each with its own pad and I do small sections at a time.
I have also tried products like "RejeX" or "Nu Finish". I have tried RejeX, and didn't think it held up as well, or looked as good as the Colinite. The top of my current 25 has something on it--and it may be NuFinish, or Poly Glow with a very thick application. The person I bought the boat from swore that it was just a "wax". I am not removing it, or waxing it to see how it holds up. Poly Glow will eventually turn yellow, and at some point need to be stripped.
Some have had the boats Ceramic coated (crystalline Si02 glass coating). I have no experience with this....lasts from 3 to 24 months depending on who you talk to.
It pays to keep the boat waxed, and help to preserve the gel coat. Most C Dorys were made with Cook Composites Gel coat, which is a top of the line product. After a certain number of years, gelcoat which is not well cared for will begin to crack and deteriorate. I once owned a Cal 46 which had been in charter service the Caribbean when the boat was new. She was 20 years old when I acquired her, and the gel coat on the cabin sides and top was shot. We had to sand it off, coat with epoxy and cover with two part Lineal polyurethane paint. The hull had also been painted in the past--so I assumed it had gone before that on the deck and cabin side. A good LP paint job will last 10 to 12 years, and will require less maintenance.
In any case, always wash the boat as soon as you can after use--especially if in salt water. You can use Tri Sodium Phosphate to remove stains from the hull. I avoid harsh acids. The TSP is available as a powder at hardware and paint stores. It is the active ingredient in may "hull stain removers".
