If the shakes are rough side out they will grab it pretty good. The challenge is to get it into the little gaps between the shakes without loading up the faces too much. The beauty of it is, unlike stains and other paint apps, 3000 on rough shakes doesnt show any trace of brush marks, so you could keep a brush handy and use only as needed. I think once you got the feel for it, it would work pretty slick. I will tell you that if you do all brushwork on a cedar shake house it is about twice as labor intensive as a clapboard sided house.