Bake and cool cake. Place cake on turntable for ease of icing. Seal loose crumbs by crumb-coating, spreading a thin layer of icing. To keep from pulling cake, thin buttercream icing with water. With long strokes, spread onto sides of cake with a metal spatula with a long blade. Crumb coat top of cake. Once icing forms crust ice sides again, then top using long firm strokes with same spatula. When second coat of icing forms a crust, smooth out with a pastry roller.