When I’m immersed in the flow of a painting, I dont like interrupting the process to clean my brush for a clear water wash, then reload it with more color. I’ve tried using two different brushes, one for paint and one for water, but I found it awkward to constantly swap the brushes back and forth to my painting hand. Instead, I fashioned a two-headed brush.
To make your own, take two brushes of equal size and cut them as shown in the illustrations (a and b) below. Be sure to allow for part of an overlapping joint on each handle. Use carpenter’s glue to connect the two brushes then clamp the joint. After the glue has dried, sand the handles to make the joint smooth. Then repaint the bare wood with a glossy enamel paint. To remind you which end to use for color, paint a ring of color near the head (c).