First I'd give it a good scrubbing with a nylon brush and some Trisodium Phosphate or a Toilet Bowl Cleaner that contains Oxalyic Acid like Sno Bol cleaner. Then let it dry for a couple of days.
[FONT=arial,hevetica]Then I'd oil it with Tung Oil. Oiling requires multiple coats. The wood will initially "drink" the oil, and thinning the first coat about 20% with mineral spirits or turpentine encourages it to penetrate the wood more deeply. By the third coat, oil will begin to stand in some areas. Wipe up excess oil with a cloth. Continue to brush on the oil and wipe away any excess until the wood is saturated. The wood should have a matte finish without any shiny spots. During the season you will need to Oil it once a week especially if it sits in the sun a lot. I would not apply a sealer since you don't want it to be slick when people stand on it.[/FONT]
