Had to use some pretty drastic cleaner on the hull to get off some dried impacted gunk after bumping an underwater obstacle! Gelcoat looks fine, smooth as a babies bum, but the shine has gone and area is now matt. An area of about 10 inches by 3 inches.
3m Finesse by hand or machine, it's a specific GRP compound. If you get hold of a good machine polisher, use a super-mop head and it'll come up better than the rest of the hull.