A brush is required on trim molding and to paint the border or "cut–in" the corners when rolling walls and ceilings. Below are some techniques for handling a paint brush and applying paint with a minimum of mess. If you need to mask to paint a straight line between two paint colors, use the instructions for painting trim molding and painting a white ceiling.
For improved control over a standard, straight cut paint brush, use a sash brush for these projects.
Hold the brush as you would a pencil or pen, grasping it around the ferrule (the metal band holding the bristles to the handle). Use the brush with the angle of the bristles pointing up.
Fill a pail about half way and load the brush by dipping it into the paint pool and lifting back up until the bristles clear the liquid. Tap the brush once or twice on the sides of the pail to work the paint in and blot any drips.
Apply the paint to the surface starting at one corner and brush in long back and forth strokes to spread the coating evenly. Don't try to spread the paint too far, before the brush starts to drag stop and reload before continuing. Start the next application a little out from the end of the first and stroke back into the wet paint to blend the two before moving on.