When painting along the trim and under ceilings, use an angled bush to get into areas that a roller can't reach. The technique is called “cutting in.”
A roller is typically better than a brush for walls and other large surface areas. Use the correct type of roller cover for the type of paint you're using.
In an area about 3’ x 3’, roll on paint in the shape of an N, from bottom left to top right. Fill the center horizontally, then lightly smooth with vertical strokes.
Painter's tape keeps paint off trim and gives clean, straight paint lines. Press down well along tape edge so paint won’t bleed. Remove tape before paint dries.
Kick back and admire your new room! Make sure walls and trim are dry before moving furniture back against the freshly painted surfaces.