When it comes to moss removal on composition roofs pressure washing is not the way to go. It looks really good yes, but the pressure pulls off so much of the grit and life from the shingles. Or when done wrong can cause leaking in your roof. We like to spray a light chemical first to loosen up the moss, and then just lightly brush it followed by a roof blow to get all the needles and other moss, debris off. Most always a gutter cleaning needs to be performed. Now is the best time for moss removal and gutter cleaning.
Here you can see in the before and after of an end result of moss removal without pressure washing.