Power washing a porch and touching up the paint?

The family that a friend babysits for was looking for someone to paint and power wash the deck. I am good with the painting but I have never power washed anything. Any advice tips or warnings would be appreciated. I assume I would power wash it THEN paint, but like I said, I'm not 100%Power washing a porch and touching up the paint?
power wash first. go for the green growth and loose paint...let dry...remove other loose paint the nomal way...prime bare wood and paintPower washing a porch and touching up the paint?
You need to be careful and test the powerwasher's tip before you use it on the deck.Try it on a piece of wood or something.You want to use a wider spray tip not a fine point tip this kind of tip can actualy cause damage and cut or make a gouge in the deck.