quick question here. roof has light coat of moss starting. put up zinc strips this summer, but i think we need to help it by taking off what is there now. what i need to know is when you put your tide detergent on roof, do you sprinkle it all over or do you put it evenly in a strip at top. this is sorta important, since this roof is black and i don't want any white spots of any kind left on it, because we didn't put it on right. need some experience, here. lots of thanks.