Painting clouds on a ceiling is best done using a wet-in-wet technique, which creates feathery, beautifully blended areas of pure sky and clouds. Begin at the horizon line with smaller clouds, making them larger and fluffier as you work your way up, with helpful tips from a professional artist in this free video on painting techniques.
How to paint clouds on the wall and up on to the ceiling. I'm going to start with a blue. I mixed a blue paint earlier just some paint and tint and I had just applied it randomly to the wall leaving areas that will become the clouds. When you are painting on the wall you are going to have a horizon so you are going to end up with smaller clouds as they reach the horizon line and larger clouds as they would go up to the ceiling. I'm going to take the same blue paint and using sort of a wet on wet technique, put them into the cloud shapes that I have formed already and as the sky reaches this level the more distance this would become lighter and that will happen when I start adding the cloud color. Well it looks pretty bright white and start bringing in my cloud formations that I had left and I think kind of like a cloud I have to drift and soften and some areas are left heavier. Stand back and take a look at what you have done to make sure it is effective. It is getting the movement that you want. It is always a good idea to make sure your ladder is secured and that it is not old and rickety and wobbly and that areas are braced. The same technique would be applied to a ceiling except for the clouds are going to be larger and bigger and billowier and they will be overhead so you won't need the distance clouds at the bottom.