For the brush part/ bristles themselves, I would strike a metal curry against it. For the leather back, once it gets pretty dirty I would end up wiping it down with a damp cloth and then conditioning it with a leather product, such as neatsfoot oil or saddle soap.
Is there any particular reason why you would like such an expensive, fancy brush?
Intermediate Rider~Learning Equitation and English Pleasure~Interested in Eventing
A horse will tell you everything you need to know about him, if you listen.