If your existing surface is gelcoat/fiberglass, try to keep it as long as possible, even if it doesn't look "new"any more. We repaired some spots of crazing & anchor fluke dings on our white foredeck with epoxy filler. UV degradation turned the epoxy dark brown, so it looked terrible and we painted it to cover it. Now it needs painting again. ARGGHH!! $$$! Gelcoat is about 10x thicker than paint, and lasts a LOT longer. Even tired gelcoat looks better than tired paint. We'd have been better off sanding the epoxy off and shooting new gelcoat, despite the expense of that. (Painting ends up costing more because you have to do the whole deck to make it look consistent, AND you have to to it again when the paint wears. ) Kiwigrip may last longer than paint, but it will still end up wearing, chafing, corroding down to the original surface unevenly, and will need re-application. You are right to ask lots of questions before taking any steps in any direction.