A concave type of trim that bridges the corner between the wall and ceiling is called coving.
1. Room should be cleared or items in the room should be covered with tarps or drop cloths.
2. The edge of the tape should be lined up with the edge of the coving so no wall is exposed.
3. The coving should be painted using a paintbrush moving the brush horizontally along the coving, and making light strokes a few inches long, working within 2-foot sections. The paint should be allowed to dry.
4. Paint the first couple of inches of ceiling adjacent to the coving with the brush if you are painting the ceiling and coving with the same color.
5. The ceiling should be painted using the roller with two coats, if you are painting both with the same color. The paint should be allowed to dry in between coats.