How to Clean a Shaving Brush using Borax Substitute. Shaving brushes need regular maintenance to avoid bacteria growth and product build up, as well as bent and loose bristles. They can be cleaned quickly and easily using Borax Substitute. A shaving brush should be deep cleaned every 2 - 3 months as oils from your face and product build up can affect the absorbency of the bristles and how effective the brush is. For more tips and advice using natural and traditional products for Dri-Pak, visit www.dri-pak.co.uk