Badger brush: Even if you decide to use white vinegar, use it diluted 1/5 with water. Do NOT leave the brush for a long time inside the vinegar. Use only if there is a build up soap inside the knot.
It shouldn't though, if you rinse it carefully with plenty of warm water after use.
However, I would use only hair shampoo.
With the synthetics is more simple, even if I tend to overdo it with a new one.
My method:
- Quick rinse with mild dish detergent
- Rub the brush on Dettol bar soap and rinse
- Wash it with hair shampoo, rinse it and microfiber towel dry.