Can TotalBoat Gelcoat be flattened to a satin finish?

TotalBoat Gelcoat's finish can be reduced from gloss, simply by wet sanding the surface. The grit of wet sand paper will define the finished gloss level. The finer the grit (higher the grit number), the higher the gloss. A good starting range of wet sand paper is 1500- to 4000-grit. 

It is important to understand that reducing the gloss of a gelcoat material reduces the UV reflectiveness, and it will absorb more UV, leading to faster oxidation. Concurrently, it also is more prone to staining in the microscopic grooves and cavities from the wet sanding.