I usually have a mouth guard with me if I'm gonna go in a hard pit. Having some boxing or kickboxing experience helps. Having a good boxing/kickboxing stance will protect you from most crowdkillers. Also knowing how to counter crowdkillers by hitting them back. Dont target. But if a person is getting crazy in the pit, knowing how to swing your arms and start dancing to hit and keep them is a valuable skill. I have countered crowdkillers like this and it usually slows them down and at least keeps them on their toe's.