Oh hey I saw something about this recently. I read the medicine subreddit cuz I’m a weirdo. Dunno if this will be helpful, but here’s what I saw one doctor type person post:
Have them toss out half a bottle of afrin and mix with saline, use that for a week, then toss out half again and dilute again with saline, use for a week, continue diluting until they feel ready to go off. Sometimes a short oral pred burst is needed too unfortunately