Aquash Water Brush Product Description. The Water Brush has a little water reservoir in the barrel. It can be refilled easily and as often as desired. By pressing the barrel, water will be delivered via the tip. Hence it is a perfect tool to create different aquarelle techniques or to mix colours. Product Description, Ideal for use on the move. Ideal for producing aquarelle or water colour-style painting at any time, in any place, without the need for extra equipment. Extremely durable nylon tip. Contains water tank with 10ml capacity. Pack includes 3 different tip sizes: fine, medium or broad.