For added emphasis when DW says clean, he means CLEAN! A sloppy job will lead to spray pattern problems that end up giving you fits with all the troubles you mentioned. As an infrequent painter I find it very usefull to spend extra time with gun setup and test sprays on a large sheet of cardboard or plywood before taking gun to the vehicle. If the pattern isn't right, or the fluid volume is off, air pressure at the gun too high/low, it's better to spend time and material on a board rather than on the car and then having a REAL mess to clean up/repair/undo. Pros like DW can set the gun in their sleep for whatever material or conditions they face, that's what doing it all day, every day prepares you for. But a weekend warrior needs to be more thoughtful.