How to cover dark paint

Covering dark paint with a lighter paint is not that hard.
Sound preparation is always the key to achieving a long lasting and quality finish. First, clear the work area as much as possible. If anything remains, such as heavy furniture then cover well with a thick dust-sheep. Also cover floors with dust-sheets to protect from paint splatter and accidental spills.
Make sure there is adequate light to see by. A finished job in the dim light may look good, but the daylight will show up all the flaws.

Good ventilation is a must.
Interior paint will be oil or water based. In either case it will need flatting down: sanding is dusty so wear a mask. For walls use a medium sandpaper to take out the pits and irregularities. Any loose paint can be scraped off. If no woodwork is to be done then mask off with decorator's masking tape. Walls that have very loose or dusty paintwork can be sealed using a PVA sealer of five parts of water to one part PVA, or use a proprietary sealer from your local decorating store.
Tobacco stained ceilings must be washed and sealed to prevent bleed-through. An oil based undercoat can be used, or a sealer recommended by your local paint store. Leave this to dry overnight.

When the surface is ready to paint, set up your roller paint tray and roller with long handle, and paint brush for cutting in. Make sure the paint is well stirred. Pour only enough paint in the tray to cover the well of the tray.
Greasy surfaces such as behind the cooker will have to be scraped flat, washed off clean before painting.
Starting in one corner of the wall, roll the roller up and down the walls to ensure even coverage. Rolling back over your work evens out the paint and takes out paint lines. Paint the walls first with the roller. Then, using your paint brush cut in the parts that can't be done with the roller. On very dark surfaces three coats will be needed, using good quality emulsion paint. Extra coats may be needed if using a cheap, thin paint. Leave each coat to dry properly.

Reading the label on the paint container will say how much time the paint takes to dry.
On inspection in the daylight, the cutting in around the edges can sometimes look darker. One more coat on these areas will usually cover and take away the shading. Covering dark paint usually takes at least three coats of paint.
If any bleed through of stains occurs then these will need to be covered by oil based undercoat or proprietary stain blocker. Re-roll these areas to blend in.
Woodwork that has oil based gloss must be flatted down with fine to medium sandpaper, then cleaned with a damp cloth to remove dust.
A vacuum cleaner can help to remove dust. Any irregularities in the woodwork or wall can be filled with a powder filler mixed with water and sanded flat when dry. Paint gloss when prepared, with two coats of an oil based undercoat. Finish with one coat of gloss.
To re-cap: a good preparation and set-up, filling, sanding, dusting, use of correct paints, and three coats of paint is needed to achieve a satisfactory finish that covers dark paint well.
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