I would think that just shooting a jug of water with a blank and have it disintegrate should be enough to wake a few folks up.
This is another reason I am in favor again of starting the event with everyone (both sides) assembled, and have the event organizers brief and inspect everyone at once. I used to be in favor of starting each side off on opposite ends, not knowing who you'll be facing until the battle, but one big briefing works better. Besides, if each side is segregated, the vendors can't effectively sell their wares, and pre- and post-battle camaraderie between sides is killed. What we need is a little more unity and sharing of ideas!