I can tell you how not to do it. At about 35 years of steady use my Hoffritz For Cutlery badger knot fell into the sink when I was shaking the water out. I took a tube of silicone sealant to do the job. Probably not a bad thing but I used a bit too much and excess came out onto the bristles at the base of the handle. Not enough to effect the utility of the brush but I see it every time I pick it up. If I had it to do over I'd use much less material and it would be epoxy or gorilla glue.