Often traditional painting methods use multiple coats of the desired paint color. This is a wasteful practice requiring much more finish paint and a lot more time plus the physical effort of getting the done.
This is what I do to paint over dark colors and get the job done quickly and on budget.
First, make sure you are dealing with latex paint. If you are unsure do a test with a clean white rag and denatured alcohol. Saturate a small area of the rag and lightly rub the painted surface. If the paint is water based it will become soft and a little will be on the rag. Use a white rag as dark paint colors will show better.
100% acrylic is best for painting over dark colors as it is thick and will dry fast. If you are dealing with oil base paint it must be primed before painting. The primer should be tinted to approximate your finish color. This will promote better coverage of the finish paint and reduce the time it will take to paint over dark colors.
Now it's time to do some painting. The best paint colors for coverage are off-whites with a little bit of tan. The addition of brown pigments will make the paint cover better.
For the first and possibly second coat, if the original color is really hard to cover, use a top quality exterior flat paint mixed to match your desired finish color. The exterior flat will cover better than interior flat or satin and infinitely better than any semi-gloss. Plus it dries faster.
Apply the exterior paint until you have near perfect coverage. This could take two coats if the original color is very dark or intense. The second coat can be applied after the first has dried to the touch. It is best to allow this layer or two of paint to dry over night.
Now simply apply your chosen finish paint over top the exterior paint. Since you now have a perfect colored background only one coat of finish paint is needed. I recommend a satin sheen in most living areas and a semi-gloss in bathrooms and the kitchen.
Painting over dark colors will take more than a singe coat of paint. This is unavoidable. By following these ideas the amount of coats and effort it will take can be reduced, reducing the time it takes and the cost to paint over dark colors.
Give the dark color a "wash coat primer" using the new finish coat paint… it will cover enough and dry faster.. then finish coat it again with the same paint, after the "wash coat" drys, applying it accurately as you do in finishing coating…
You could use a product called Aura by Benjamin Moore it is seft-priming and has excellent coverage.