Pro painters know how to properly load a brush for cutting in, for outside corners, open wall space and trim details. Not enough paint means you’ll over work it trying to get the coverage. Too much paint means you’ll lack control on your edges and eventually have a dripping mess on your hands.
Pro painters know how to load the brush and how to get consistent coverage and leveling by applying paint with the right speed and pressure. It’s a pro move. Your best pro move might be to call the Paint Doctor to avoid those unsightly brush marks.