Talke to the folks at Porter paint. There is paint and most likely sealers on the market to take care of issues such as this. I know that such paints are used in food service areas to prevent slips and falls.

Hall is right about cleaning the deck only I would add dawn dish liquid to the water bleach mix and scrub it with a broom which I have done. By doing so it well make a big improvement on the deck by itself.

DA