Hello Dragon,
I firmly support Reservist1's view re. hair plumes, either horsehair or buffalo/yak hair. Shampooing with a mild shampoo in warm water works very well. Another product available via the horsey set is called "Mane and Tail."
I would caution you, though, if you do decide to separate the plume from its trichter, proceed with great caution. Quite often the anchoring mechanism for the hair has perished and you may wind up with a handful of hair and a very bald plume. And, they're the Devil's own to rebuild.
In the case of feather plumes, which is what I think I am looking at in your avatar, you may be best to leave well enough alone. I don't think the anchoring mechanisms for feather plumes are all that secure and many plumes were built by splicing together shorter lengths of feather to make long plumes. You risk severely shortening your feather plume if the splices come unstuck.
Good luck with it.
Cheers,
Laurie