Thanks. Northeast MD ? We're on Bohemia. I'm on a budget, looking at below.
I would worry about that approach. Walnut shells are biodegradable and would likely rot over a relatively short period of time. My guess is the paint would fail shortly afterwords. It is the biodegradable character that makes ground walnut shells desirable for sandblasting. Any inhaled "dust" will eventually breakdown in your lungs and not lead to siliconosis of the lungs.
I have used pool products on boats before. I once restored a very badly damaged hull on a Coronado 23. After grinding the bottom to clean glass, I applied two coats of epoxy barrier coat from my local paint store. The barrier coat was sold for pools. It did a good job and held up for the three remaining years I owned the boat. It was only half the price of barrier coat sold for "marine" purposes. I would not recommend this for a higher end boat though.... just sayin'. But if you are on a budget I think @Don S/V ILLusion 's idea to use a non-skid for pools is worth exploring.
No but if you try it, please post a report of how it worked. Sounds interesting but I can also imagine a lot of reasons why it could fail miserably. If it were my boat, I'd test that idea on a very small section and see how it worked out before doing the entire deck.