Hello from the great northwest -- where moss is a way of life!!!! . . . . .
Pressure washing is very temporary and can damage surfaces. Many of us in the Seattle area use a product called -- and it's not a joke -- "Slimy Green and Slippery Black" which can be purchased through Ace Hardware -- it is about $10/gallon and mixed with equal parts of water and sprayed on with a simple sprayer -- the kind you pump and apply with a wand -- it works like magic in about a minute or two -- may require a little light brushing -- but is "marvelous" -- and it does not harm plants or grass!!!!! Another tip is to moisten the area and sprinkle with good old "Arm and Hammer" baking soda. Brush good and rinse.
Both work great -- I've done both. But pressure washing alone is very temporary -- we tried it this year and you can still see the moss deep in the crevices -- and the cost of renting the pressure washer was a little more than buying Slimy Green and Slippery black!!!!