I've use Corte Clean for about 4 years and it really brings my deck back to life after a miserable Chicago winter. I spray it on and let the rain activate the cleaning process. Using it 2x a year really keeps it looking great. If there are a few dark, moldy spots left after the winter, I give them another shot and wait for the rain, unless I'm really impatient. That one time I just sprayed it on again, let it "work" for a few minutes, and then used an old push broom to brush over them. However, since I'm basically lazy and would rather do something else - I just pop a suds and wait for the rain.