I form topiary frames for myself and my friends. As the bushes are growing, I push the new growth that protrudes out of the frame back inside.I try to guide it toward the areas that are not filled in. When large areas are filled in I start trimming the new growth even with the contour of the frame. I do my trimming with an old sewing scissors. I have seen advertisements for scissors that are designed especially for this. I'm quite satisfied with using this scissors.