After removing glue and loosening hair enough, wipe off moisture so as to sharpen hair gently with paper or cloth finally.
When writing starts without wiping off the moisture sufficiently, the sumi ink diminishes and the written letter blurs out.
If you do not wet the hair and try to loosen your brush, the hair may cut off or sumi ink does not penetrate into hair and it becomes a faint letter.
Soften a small brush
Wash only the tip of the hair and loosen it with your fingers. Be sure not to loosen up to the root. If you loosen it to the root, the hair spreads and you cannot draw a thin line.