are there different grades of boar hair like with badger hair ?
If a badger has different types of hair around the body, and we humans has as well, I think it would be fair to presume that a pig also has different types.
As mentioned above, Semogue grade their hair, and from personal experience I can say; there is a difference in the way the hairs perform.
However a domestic boar... (boar = male pig) only has hair in limited places that is long enough to use for a brush. ...(on the back and side of its body) the hair on the neck and butt and belly of a boar is to short to use. The hair on the back is a bit longer and more course than the hair on the side and it may vary a bit somewhere in between those areas.
This may also vary a bit depending on the breed of pig.