I just bought a 1972 43' Burnscraft houseboat which is all fiberglass. The outside has not been touched in 4-6 years. It is all fiberglass. Other than being dark, there are also some kind of spider like lichens also on the surface. I can scratch off the lichens with the back of my wood scrub brush , and have been using toilet bowl cleaner to get to the original finish (almost like new). This is VERY hard work for me at 60. I am trying muratic acid this weekend in a remote area. Any other suggestions?