You are searching for a "Holy Grail". While there are some chems, under some circumstances, that will do this, the likelihood of streaking the siding is too high for me. I prefer Simple Green (for price and availability and least likely to strip the finish) and on newer gutters, do not need to brush, only apply and rinse. Personally, I don't have a problem working a brush on a 24' extension pole. (I wash the house and gutters with my usual housewash mix first to remove all but the "streaks", then wash the gutters when I rinse the house.)