LOL MakoMike, I know someone who rolled their deck with grey non aerobic cure gelcoat, luckily, hanging off the hullsides and using a long handled roller he applied some aerobic cure gelcoat over the old stuff and that worked well as it cured the underneath layer.
I think there's two avenues to this. You can roll the gelcoat on with the nonskid particles mixed in with it, or you can roll it on and then sprinkle non-skid over the wet gelcoat, wait until that cure and apply a second coat of gelcoat over that. Thats what I did with my boat, the difference being my deck was painted with awlgrip.