It's serious, but there's the possibility that Plasti-Dip might get into the interior of the button and insulate it so it doesn't work. You need sealed buttons. Some surface-mount buttons are sealed.[1] Many are not. I was thinking more from the point of view of what simple manufacturing step could the maker add to package the thing. Shrink-tube sounds good, although it might hold the button down if shrunk too hard.

[1] https://www.omron.com/ecb/products/sw/24/b3s.html