Carry all furniture and accessories out of the room, or push against the perimeter of the wall. Ensure you have enough working space directly under the ceiling to reach all areas. Place drop cloths on the floor or lay out plastic tarps. Set up your ladder or scaffolding to test that you can reach all areas.
Place painter's tape along the edge or border of any surfaces touching the ceiling. Rub the painter's tape well to ensure it is strongly adhering to the surface.
Wipe down the ceiling with a soft rag to remove dust. Use a small amount of water and all-purpose spray cleaner if any areas are hard to to clean or stains are stubborn.
Take a drywall trowel and add a large amount of joint compound onto the tool's blade. Swipe the blade across the surface to smooth and skim the ceiling. Hold the edge of the tool against the ceiling surface. Apply the joint compound to the entire ceiling and let dry for about 24 hours.
Sand the entire ceiling with medium grit sand paper attached to a sanding pole. Repeat the plaster technique, allowing to dry one day between each layer. Use the drywall trowel to skim a smooth texture onto the wall or to add additional heavy texture.
Paint the entire ceiling with flat latex paint when you are finished adding your plaster layers. Flat paint decreases light glare and does not show reflection.