Bocals do need to be cleaned regularly, and a bocal brush is an essential tool for this. This brush features a soft nylon bristle brush at the end of a long flexible shaft. Every part is carefully made to prevent any scratching of the inside of the bocal.
Use this brush in combination with warm water running through the bocal. Soaking the bocal briefly in water with dishwashing detergent and using the brush is also good. Be sure to re-apply cork grease after washing the bocal.