Angels and demons, though immortal, shave. They are men, after all.
Michael uses a a straight razor. He does not like mirrors.
Samael, always hungover, draws 666s in the shaving cream and sings like Tom Waits. He likes to practice his smirk.
Gabriel, the hip one, uses an electric razor so his skin is cherub-soft. Metatron has a beard. Most archangels are clean shaven. It goes along with the professional environment and hierarchy as old as dirt.
Demons are another matter. Most follow their fancies, excluding Beelzebub.
Beelzebub never whistles. His bathroom is spotless and silent. Like Michael, he does not smile. He stares into the dusky mirror and makes clean, precise cuts with his sword. The foam blends with his off-white skin and iced hair, which is sensibly cropped.