I've been using gutter Zap for the past couple of years, which works great, but the price is high. I started added power house from sunbrite to my house wash mix and found that the gutters are coming a lot cleaner, so I tried using it on the gutter exteriors and it works good. I use a brush on a pole and then rinse. If we are cleaning the debris from the gutters then we will mix it 50/50 in a spray bottle, and clean it up close with a microfiber cloth. They come out looking like new. Power house is way cheaper than gutter zap especially if you buy 55 gallons. You get free shipping if you have an order over 600.00, and no I don't work for Sunbrite.