Haha, years ago when I was in nursing school living in a dorm,
toothpaste was "the" way to fill in holes. All of the rooms had lovely
institutional green paint, and there was a toothpaste brand that matched
it almost exactly. So yeah, the "single ladies" theory is pretty
accurate, LOL.

Spackle it with 2 or 3 coats is the right way, forget the toothpaste
(I think single women moving out of apartments thought of that one).
3 inch taping knife should be fine.