Brush on a paper towel to remove the excess colour. Immerse the bristles of your brush in warm water without covering the metal part. Squeeze some mild shampoo into your hand. Swirl the brush in your palm gently. Hold the brush, bristles down, under running water until the water runs clear. Gently squeeze out the excess water. Reshape bristles and let the brushes dry hanging over the edge of your sink overnight.
