Remove all excess paint from the brush by squeezing out the paint from the inner bristles. Move from the handle outwards. A preferred way of doing this is to use newspaper or a metal edge. Do not use paper towels, as this will result in lint clumping in the bristles, making the work even harder. Be careful not to pull excessively hard, as the bristles may come out.
Place a few fluid ounces of a paint solvent into a metal or glass container. Plastic containers could potentially dissolve when coming into contact with the solvent. Common solvents include mineral spirits, acetone and lacquer thinner. Swirl the bristles in the solvent until completely saturated and thinned paint comes out freely.
Rinse the brush under running water. If the bristles still have a great deal of paint, repeat step two. When the paint is removed from the brush, the bristles will likely still be tinted by the color of the paint.
Clean the bristles with liquid soap. Hand soap will work, although a small amount dish soap will probably be easier to work with. Give the brush a final rinse once most of the coloration has been removed from the bristles.
Comb the bristles to prevent them from clumping together. This will ensure that the brush maintains its ability to hold paint and spread it evenly. Shake off excess water and allow the brush to air-dry before using it again.