Here is one technique I use for painting 6 panel doors to combat hot or windy days without compromising the smooth factory finish. This is the exterior side of an entry door. The door in this video has one coat of black paint, then one coat of Fortis and now in the video is a third coat on this fiberglass door. Notice how there is virtually no trace it was painted with a brush even after 3 coats.
This method allows each section of the door to be painted without rushing to keep wet edges.