Many people have fiberglass items that require cleaning as part of regular appearance maintenance. Figuring out what materials and cleaning agents to use can be difficult.
When people inquire with me, I point them in two different directions.
One direction is to consider household cleaners, especially those for bathrooms. Fiberglass bathtubs are exposed to many chemicals and dirty water, etc. They are prone to staining due to the nature of their application and exposures. Many fine products have been developed to enable homeowners to clean and maintain their bathtubs in a reliable fashion. These products are easily found in grocery stores.
Another direction that can identify good methods to improve the finish of fiberglass gelcoated structures is the materials and methods of the Autobody industry. Automotive paint shares many properties similar to gelcoat. Dirt, grime, and scratches can be removed from gelcoat in many of the same ways as painted surfaces. The same sandpapers, sanding tools, buffing compounds, and buffers can be used to improve gelcoated surfaces.
Working with surface coatings such as paint and gelcoat can produce rewarding results. One caution when sanding, polishing, and buffing these surfaces is to maintain caution regarding excessive removal of these coatings. Sanding and buffing removes microscopic layers of material.
Exposing layers below the outermost ones can produce disastrous results which may require major expense in repair. New layers of paint or gelcoat will need to be applied to restore the integrity and appearance of the original coating.
Expensive specialty cleaners for boats and RVs might seem necessary, but I am betting that less expensive alternatives from the bathroom and body shop will do just as good of a job.