Rosin with cloth. Ideal for the psaltery, rebec and dilruba. When your rosin is new, rough up the surface with a file, knife or edge of a key. Do not draw the bow back and forth across the rosin; this will result in ruts in your rosin. To avoid ruts, and to wear the rosin evenly, draw the hair of the bow across the rosin in tight little circles. Make sure to cover all the hairs, the full length of the bow. You have enough rosin when the hairs develop a white, dull, build-up. Before you play, use your thumb nail to flick the hairs of the bow to remove the excess rosin.