The facial cleansing brush is cleaned quite automatically with each use, by the mild surfactant of the wash piece. It is therefore not comparable with powder brushes in terms of its bacterial inner life.
However, we recommend spraying the "Facial Cleansing Brush" with a brush disinfectant spray (available at most drug stores) once a week.
If you've been using your brush for many months, you can wash it out with liquid detergent as needed and rinse with plain water.