Deck refinish, 2 part paint, awlgrip, or gelcoat?

[duefocena]

I had great luck with Interlux Brightside and window screen. Painted a first coat with roller and taped the waterways once dried. Cut regular window screen in the shape of the non skid areas. Layed the screen down taping overlapping ends and applied a coat over the screen. Waited until the paint was tacky and then lifted it revealing an almost exact match of the original non skid. If it stands too proud you can knock it down with some 100 grit. Unlike the "mix sand with paint" method you can always sand it off and easily match up screen "repairs". Sanding off the deck that has been done with sand/paint mixture is something I only want to do once. Sand vs Sand is a lot of dust and little progress.

[brianlara 3]

Very important to consider exactly what gelcoat really is.
Intended to give cosmetic appeal to fibreglass mouldings (like your deck), g/c is nothing more than polyester resin thickened with...wait..talc, talcum powder..baby powder.
Commercial body filler is, usually, ditto but much thicker. Body filler sucks when compared to my old 'lead wiping' training.
Talc is very absorbent and ABLATIVE as our nether regions know .
So I personally wouldn't thicken it any further.
If you put it on really thick (to hell with the cost), then when it gets a bit shiny/slippery in places you can always roughen it up.
Damn the weight, the cost...sand the old surface roughly, toss it on with a rough roller and it'll be there forever.
FWIW, 50 years ago worked 6 months in the f/glassing shop/ tourist coaches.