Use a 120-grit sand paper to smooth away any old brush marks from a previous paint job, previous drips and any other blemishes. If the surface is supposed to be textured, skip this step.
Add a flow extender and leveling additive to the latex paint. It helps the paint spread out more evenly, thereby reducing or eliminating brush strokes as well as roller strokes.
If the paint label states not to add an additive, do not. Also, do not add a flow extender and leveling additive if you are painting on stucco.
Choose a high-quality, nylon-bristle brush to paint latex paint. Using a 2-1/2 inch brush gives you better control.
Use the brush to cut in along the edges of a large surface. Otherwise, use a roller whenever possible.
Dip the brush in the paint, then scrape the excess off on the edge of the tray so you do not have too much paint on the brush.
Paint along the edges in small sections using the paintbrush. Then, roll that area of the wall before the paint dries, getting as close to the edge as possible.
This is a trick that reduces brush marks. Move on to the next area and repeat.