To avoid cleaning varnishing brushes that are in constant use. First drill a hole through the handles of the brushes. Then suspend them from a wooden or metal rod in equal parts of linseed oil and turpentine substitute.
The bristles of the brushes must be completely covered by the liquid without touching the bottom of the container. If the bristles rest on the bottom, they will pick up the residue of the varnish that settles there and will also become permanently curved. The mixture will need to be renewed every two to three weeks.