Clear off all countertops. Remove rugs, wall hangings and any bath supplies from your bathtub or shower. Completely cover your vanities, tub or shower and floors with drop cloths. Paint is more likely to splatter and some of the texture may fall while while you are painting the ceiling.
Apply painter's tape on the top edge of your walls where they meet the ceiling. Using painter's tape will keep the paint off the wall and make cutting the ceiling easier.
Fill your paint pot no more than half full with the shellac-based primer. Use the paint brush to prime the edge of the ceiling all the way around the room. Brush the paint on in one direction and not back and forth. Brushing back and forth will begin to pull the texture off the ceiling.
Fill your paint tray with primer and use a roller to apply the primer to the entire surface of the ceiling. Roll the primer in one direction only. If you roll back and forth in the same area, you will pull the texture off the ceiling. The reason for using shellac-based primer is that it dries quickly and will not saturate the texture. Popcorn texture has a bonding agent that allows it adhere to the ceiling. When the bonding agent gets wet, the texture will in some cases just fall off the ceiling, or roll around in your roller pad.
Allow the primer to dry according to the manufacturer's instructions. A minimum of three to four hours should be allowed. Clean your paint brush, paint pot and tray with paint thinner, then throw away the roller pad.
Apply a cover coat of paint to your ceiling when the primer has completely dried. Again, brush and roll in one direction. The primer will stop the paint from saturating the bonding agent and make it less likely to pull the texture off the ceiling while you are painting.