Pour warm water into a bowl and add a few drops of gentle shampoo (preferably one without conditioner). Swish the water with the brush to create some suds, then soak the brush head into the water and wait for about ten minutes. (Skip this step if you’re using a wooden hairbrush. I wouldn’t recommend soaking it, as water can damage the material. Instead, dip a clean old toothbrush in warm soapy water and scrub gently between the bristles.)

Once the ten minutes are up, remove your hairbrush from the water and inspect it for any remaining lint.

Use a clean, dry toothbrush to sweep both vertically and horizontally between the bristles to make sure that you get rid of all the lint. 

Replace the soapy water in the bowl with clean, warm water. Soak the brush head in the water, rinse thoroughly, then shake out the excess water. (Quickly rinse wooden brushes or hairbrushes with natural bristles under warm running water instead of soaking them.)

If you use a synthetic brush, combine one part rubbing alcohol and one part water in a bowl. Dip your hairbrush in the mixture, pat dry with a paper towel, then place face down on a clean towel to dry. (If you have a natural bristle brush, lightly spray the surface with disinfectant spray, place on a clean towel with the bristles down, and allow to air-dry.)