Paint the Room With Shoulder-Width Strokes for a Thicker Coat.
Painting a room may seem like a fairly straightforward task, but loose brush strokes can lead to unevenness or inconsistencies. Draw with strokes shoulder-width apart for easy, simple, and above all evenness.
Some people suggest that you draw in a W or V, or just draw back and forth horizontally. All of these suggestions are based on the same fundamental principle – paint in small, manageable areas. If the entire surface is not covered before the paint is dry, subsequent coats will not apply smoothly. It should be noted that this tip works best if you are drawing by hand. If you are using a roller, wide (but still smooth) strokes are better for an even finish. The article below provides many more helpful tips for improving your drawing.
Get Rid of Pain in Painting: 5 Rules to Follow to Achieve Professional Results | Apartment therapy