50 % coverage on every pass. Some youtube videos are good, and some are not. Beware. When we are spraying walls, my first pass is half on the wall, half on the ceiling (mask as necessary). I center the spray pattern on the corner between the ceiling and wall. Next pass, the top of your spray pattern should be at the corner, so your second pass will now have 100% coverage on the top half of the pass and the lower half is 50% coverage. Each pass after that, I am centering the fan on bottom edge of the previous pass. The gun should stay perpendicular to the wall always. Do not sway your hand as you move from one side to the other. It should also stay an equal distance from the surface while remaining perpendicular for the entire pass. If you sway or turn your hand as you're spraying, you will make smiles and have uneven coverage. You should also be moving at the beginning of each pass before you pull the trigger and you don't stop until after you have released the trigger. Otherwise, you will be loading up the wall at the beginning and end of each section if you are not moving or just keep it triggered. I have seen videos of guys not doing this. It is poor technique. As you get more experience and see these things happen, there are times when you may break some of these rules for different situations, but it takes experience.