Bummer about the deck.
Here's what I would do...
Do a search on stipple rolling gelcoat. Basically, you thicken gel with something like 404 high density filler until it's to your required consistency, and roll it on with a foam roller. The thicker you mix the gel the bigger the texture, the thinner the finer. Once the gel kicks, take a block with 80G paper and knock off the peaks. Thick milkshake consistency works well.
Mask the deck with some fine line tape to make a professional looking pattern. I've even darkened the deck gel with a drop or two of pigment to set them off. Be sure to pull off the tape before the gel goes off. Be sure to remember the quantities of filler and pigment, so that you can reproduce the results if need be.
The texture looks like this: