Basically, you have two types of decks...stained and natural wood...I will presume we're talking about natural wood.
I have several good techniques, some are better suited to the level of weathering you want on your deck.
For a shiny clean newly holystoned teak deck... Pollyscale Concrete with a light grey wash, followed by a light drybrushing of PollyScale Teak, Vallejo Sand, or Tamiya Buff.
For a weathered deck, Pollyscale OLD Concrete, followed by a wash of Chestnut Ink, Burnt Umber, or Black. Don't drybrush anything over the top. Once it's dry, give it another wash with a thinned version of your base coat, Old Concrete.
Experiment a bit first to see which effect you like best.
Jeff