...like how to 'kill' the undead, but this is pretty much how it played out in my dream.

Chalk (or crayon, or other not-so-easy-to-remove marker) applied to the head. If someone's launching weapons, they have to 'dust' the weapon first, but it could be feasible.

Oh, also: hi! We talked for a few hours about comics at the flatwarming the other weekend :D