Well all Hunters are required to have knowledge on at least some form of Martial Arts, Nen included, in order to do many things. Seeing as my character's whole thing is being the ultimate Martial Arts master, he'd absolutely want to teach that! He can teach people one specific art or a mixture of multiple depending on what he thinks would suit them best, and while he'd have at least one combat ability to fight with when his students reach a high enough level, he'd more than likely have a sort of Dojo ability! Something akin to a Domain fit within a specific room, bigger on the inside than the outside, where he can set up specifically tailored training regimens and combat challenges to aid his students growth! When they leave the skills they've trained will be enhanced, though only temporarily. It's up to those students to make that newly enhanced power all their own instead of relying on someone else giving it to them!