Gelcoat vs. paint
Steve and I have been debating this for what now, six years? He always advocates gelcoat and I like paint. But it comes down to cost.I have seen only a few decks redone with gelcoat. They were beautiful. But they were done by very expensive professionals with the right equipment, spray guns among others.For DIY you cannot beat paint. I used Toplac, Interlux's best one-part polyurethane, for the white. Actually I mixed some off-white and white to cut the sheen. My first attempt with non-skid was with Interlux Brightside and mixing my own Interlux grit. It has held up well but I plan to repaint with Interlux Interdeck, an already mixed non-skid. The picture is of a new color I tested on the anchor locker. Not sure I like it.I think that you mean the decks, the topsides are the sides of the boat. If you mean the decks then, unless the current non-skid is very loose, all that is required is good prep. Just sand agressively and anything that remains can be painted over. The final sanding of the non-skid can be #80 but the gelcoat should be sanded smooth. You might finish with #600 before you paint.The very best DIY finish without a spray gun takes two people. Then you can use a two-part polyurethane. But it sets up so fast that you need one to roll and one to follow with a good brush to "tip".It helps to cut the deck into small sections. When you paint the white(easy because no taping is required) put some 1" diagonals to split up the deck. I have one from the chain locker straight to the cabin trunk to separate the two halves of the boat. Then another at the shrouds. This way you don't have to paint continuously to keep a wet edge. And you definitely have to keep a wet edge. Post some pics when you are done.