One of the biggest reasons to use a face mask brush is to prevent any dirt, oil or germs that may be hanging out on your hands from soiling your clean face. This can cause unwanted breakouts, which is what you’re hoping to avoid by using a face mask in the first place! And when you use a face mask brush, it should be as clean as possible for the same reason. Just wash with warm water, and add a gentle cleanser if needed. Consider a two-pack of brushes in order to clean one while using the other.