My homestay students are pigs. I just spent over an hour in their disgusting filth. I'm worried a big ball of stuff will go down the line and plug everything.
Guys are even cutting their own hair in the sink these days.
The way to keep whiskers out of a sink is…
Remove the "vanity" mirror from over the sink to another location… and the whiskers will follow.
Choose another location where cleanup is easier for the "janitor." Maybe locate it over a trash receptacle so the "message" is also communicated.
Get a large towel or plastic sheeting, or large trash bag. Attach two suction cups to the right and left side bottom edge. Stick suction cups to bathroom mirror. Attach other end around neck of shaver with large safety pin. After shave, the shaver can remove fom around neck, detach suction cups from mirror and shake out over trash can. It's like a bib that catches the whiskers from falling into sink.