Cleaning paint brushes should happen immediately after use so as not to let the paint harden. Make sure to use the proper solution/solvent (water, mineral spirits, lacquer thinner, denatured alcohol) to rinse the brush.
Water Base Paint
When cleaning paint brushes containing water base paint (acrylic, latex, and acrylic emulsion), it is preferable to use a solution of warm water and soap. Cold water can also be used if warm water and soap are not available.
Rinse the brush several times to ensure that you have cleaned all the paint that may have collected in the heel and around the spacers as well as all the paint on the bristles. After the initial rinses are completed, rinse again with the brush handle pointing downward. Firmly squeeze the bristles to force the rinse toward the heel. This will clean the paint that has collected in the heel and around the ferrule. Repeat until the rinsing solution appears clear.
If the paint brush contains large amounts of pigments, it may need to be rinsed with mineral spirits after their initial cleaning with water. The mineral spirits will remove the excess pigments that the water does not remove.
Solvent Base Paint
Cleaning paint brushes with a solvent base paint requires using the proper solvent. Rinsing with the wrong solvent could damage the brush. The following is a list of paints with their corresponding solvents:
When cleaning paint brushes with oil base and solvent base paints, you should prepare three or four batches of solvent. Place 6 to 8 ounces of solvent in small, clean plastic buckets. Try to avoid using too much solvent, because of the difficulty of disposal. Rinsing several times with the first solvent batch, removes the majority of the paint from the bristles. This causes the first batch of solvent to become somewhat concentrated with paint. The subsequent rinses in the other solvent batches, remove the remaining paint. The final batch of solvent should appear to be almost clear because most of the paint has already been removed from the brush.
Cleaning solvents can be re-used another day for rinsing brushes, but they need to be stored properly so as not to present a hazard.
If some paint has dried on the bristles of the brush and does not clean off during the rinsing process, use a fine bristle wire brush to remove it. This is done with a similar motion to that of combing the brush. Acrylic paints easily stick to brushes containing polyester filaments. They often need to be wire brushed. You might consider cleaning your paint brush a couple times a day. Before storage, comb the bristles, with a metal comb, to straighten and align them.
Some Things to Avoid
Do not leave the paint brush soaking in paint for prolonged periods of time.
Do not let the brush stand on end while resting in the paint.
Do not leave the paint brush soaking in water or solvent.
Do not store the brush resting on its bristles.
After thoroughly cleaning paint brushes, they should be stored properly. Professional grade paint brushes come with a cardboard sleeve. This sleeve should be used to protect the bristles and keep them aligned during storage. It is a good idea to hang the brush from a hook or a nail, so as not to put any pressure on the bristles. If this is not possible, you should store the brush in a flat position.