With the brush, you avoid the use of water and soap. The cap becomes free of dust and dirt, which is good because a dust-coated fabric and suede will just attract more dust and grime. However, use only the brush only if the material is suitable enough for brushing. For example, normal and loosely woven wool is not suitable for brushing. This will cause the wool to ripple and create pilling on the surface. If you are unsure whether the cap can be brushed then watch the Wilgart guide video on brushing a cap or hat.