Steve,
I have used a product called Woody's Wax to coat the nonskid. You might want to do a search, as many on this site have also used it. You can either power wash the deck or use soft scrub to get it really clean. Then apply Woody Wax as per the instructions. Woodys coats the nonskid and leaves a slight sheen on the deck. It does not make the deck slippery after it dries. Definitely makes cleaning the deck easier during future washings. In my climate, it lasts for about 6 weeks and requires reapplication. Just wet the deck and spray on a coat, then spread it around with a soft deck brush and let it dry.
This stuff really isn't a wax, but a coating. I wouldn't use wax on the deck as it defeats the purpose of nonskid and makes it too slippery.