premise: Apply first coat of paint to ceiling.
hypothesis: Hold the brush against the ceiling with the handle of the brush below the bristles. This will bend the bristles of the brush so the long fibers of the brush, rather than the tips, are in contact with the ceiling. Applying the brush this way will remove many of the brush marks that can be left behind by a paintbrush, and provide you with a smooth edge. Move on to the interior of the ceiling, overlapping the brushstrokes with a roller just slightly to provide a clean surface on the ceiling with no visible edge where the brushwork begins.