Painting a ceiling can be tricky, since you have to deal with the greater potential for drips or spills. Furthermore, painting wooden surfaces requires additional prep work. However, with the proper knowhow, painting a wooden ceiling is possible even for the novice painter.
Remove all furniture from the room.
Use a step ladder to reach the ceiling. Make sure you have somebody standing at ground level, holding and stabilising the base of the ladder.
Touch the wood to see if the surface is treated. If the surface is shiny and smooth to the touch, then it has likely been covered with a layer of polyurethane. This glossy treatment does not accept paint unless properly cleaned.
Wash the ceiling using a rag soaked in Tri-Sodium Phosphate (TSP) cleanser to remove unwanted oils from the polyurethane coating. Wipe off the TSP solution using a dry rag after you've washed the ceiling. TSP is not harmful to human skin, but you may still want to wear gloves because TSP has an odour that can be difficult to wash off your hands.
Sand the ceiling. For untreated, rough wood you need to use 60-grit sandpaper first. This rough sandpaper will remove large splinters and imperfections. Use 100 grit sandpaper after the raw wood has been sanded with the 60 grit paper. For treated wood, you can skip the 60 grit sanding and go straight to the 100 grit sandpaper.
Tape the edges of the ceiling using painter's tape.
Lay plastic tarps on the ground to protect your floors from accidental splatter. Gravity will naturally cause a few drips to land on the floor regardless of how careful you are, so always use tarps to be on the safe side.
Prime the ceiling using an all-purpose primer. While drywall ceilings can be painted without primer, wood ceilings are porous and require a good coat of primer for adequate coverage. Use a synthetic bristle sash brush, as recommended by handyman Bob Vila, for corners and for painting the 4 inches of ceiling closest to the wall. A paint roller is used for the rest of the ceiling.
Wait for the primer to dry. Follow the drying times provided on the primer's container. Every brand of primer has a slightly different drying time, but usually the primer is ready to accept paint after a few hours.
Apply latex paint to the ceiling, using sash brushes for edging and rollers for the main ceiling surface, just as you did with the primer.
Wait at least two hours before checking the ceiling for bare patches. Apply another coat of paint if necessary.
Step ladders are safer than freestanding ladders, but accidents can still happen. You should still always have a person on the ground to hold and stabilise the ladder as you paint.