How to paint mouldings/cornice

Mouldings come in all shapes and sizes; the most common is made from plaster but also comes in wood, polystyrene, marble and plastic.
It is usually used around the ceiling to decorate or profile the edge.
Circular mouldings decorate the middle of the ceiling where the light fitting goes.
Plaster mouldings are usually painted using a long haired bristle brush of approximately two and a half inches wide. It is always best to buy the best brush affordable, with bristle being the best, synthetic hair brushes being of inferior quality and not the best to use to get the paint into the moulding.

Very high ceilings will need a square scaffold on wheels so it can be pushed along the work. Always lock the wheels before climbing up.
For most ceilings a set of aluminium step ladders will suffice. It is always safer with two people, but painting mouldings from a scaffold or long ladders can be done alone provided you follow all safety advice.
Begin with preparation.
Move all non essential furniture away from where you will be working. Cover the work area with dust sheets to catch any paint spills. Set up your scaffold, or step ladders, or trestles with planks to walk along. Make sure there is enough light to see that the work is being done right.

Before painting, visually inspect the moulding and look for any fine cracks which will need to be filled. Mix up a powder filler, from a do-it-yourself shop or decorator's shop. Mix the paste in a square container by adding water until the powder has become firm, but not too firm. Never use ready mixed as it dries too hard for plaster mouldings.
Use a decorator's scraper for the flat parts of the moulding. Fill any cracks to the surface and leave until dry. For cracks that are on the rounded part of the moulding, a finger, or butter knife can be used.
Sand down when dry with fine sandpaper. If any filling is not the same shape as the moulding then re-fill with filler and sand down flat when dry.
It is important to get this part as good as can be before you begin painting as any flaws in the plaster will show up when the work is done.

Any flaking old paint can be scraped off and gently sanded. Moulding that has stains can be sealed with a penetrating sealer, or a water based sealer mixed with water at a five to one ratio
Almost all plaster mouldings are painted using a water based emulsion paint.
Acrylic emulsion is washable and is generally a finer finish. Almost always two coats of paint will be needed.
A two and a half inch brush will do most jobs. Use a smaller one for tight spaces. Dip your brush into the paint until half the hairs are under the paint, then remove any excess on the lip of your paint kettle or paint container.
Start in a corner and work your way around, looking back over your painting to see any missed spots or areas. Stipple the brush into the moulding, then brush off to make the paint even.
Paint may dribble down the brush onto your hands, and if so then wash off with warm water sooner rather than later.
After the work is complete, brushes can be cleaned in water. Spilled paint must be washed off immediately with water.