I have pressure washed and used Wet N Forget. Pressure washing damages the tile eventually. The Wet N Forget takes at least 4 jugs and works overtime, price went up on the jugs, it is a chemical also. In addition pressure washing risk tile cracking from somebody stepping on them. Previous to my new roof I used a pressure washing guy who always took caulking with him to repair tiles. With my new roof I recently applied Wet N Forget, not stepping on a new roof and risking damage.