Start with Simple Green. If you cant get the stains with Simple Green, follow up with something like Roll Off.
On your decks and non-skid; Another option if your on shore power is a light weight household electric power washer. Light weight being the key. Be extremely careful when using power and water.
How does Simple Green work on bird droppings?
Another thing that works well are those pressure washer wands you hook up to a hose. Can't compare it to an actual power washer, but it worked well enough for me.