The ghd Natural Bristle Radial Brush size 3 has a large barrel, (44mm) making it ideal for longer hair. The professional design helps you to achieve a salon-perfect blow dry at home. How to use ghd Natural Bristle Radial Brush Blow dry hair until it is at least 80% dry. Separate hair into small sections, then place the brush at the root and direct heat from your hairdryer towards the barrel. Keep the tension as you move the brush through your hair, directing heat at the barrel as you go.