It is important to know how to clean walls before painting for the sake of achieving the best result of the painting at the end. It should be done in several steps from simply cleaning the dust up to the scrapping of the old layers of paint from the surface of the wall.
Cloth or dusting brush can be used to clean the surface of the wall from dust, cobwebs, and also loose dirt. This will ensure that none of them will affect the painting further. Removing mould is also important in which it can also be done easily. The combination of water with either chlorine or sodium hypochlorite in 4:1 will do.
Just spray the mixture and rinse it to clean it out further. Next thing to do is to use either sandpaper or wallpaper remover to remove the old surface of the wall which could be paint or wallpaper. Be sure to get it done properly.
One last thing to do is to wash down the wall by using washing-up liquid and also hot water. This is the last crucial step to really make sure that the wall is squeaky clean before the new layer of paint is applied.