To paint the top of a baseboard, paint down from the top for five or six short strokes, then smooth over them with a single, long, smooth stroke. Then, using a painting shield or a thin piece of cardboard as a movable masker, cut in along the floor. After that, you can fill the unpainted space between with long brush strokes. Paint only 2 or 3 feet of baseboard at a time. Examine the surface for drips, spatters, and overlapped edges, and clean them up immediately. Do not wait until the entire baseboard is painted or the paint flaws will have already set.