If you can glitch into anything without kicked/killed. Do that
If not, just get atleast 5 people to a spot near safe room. When a zombie is around, YOU don't shoot. Let the others spam bullets. When they reload, zombie will try to run in. When you see them reloading, your turn to spam bullets.. Never let anyone near the legdes, if they go near.. it means they're hoping to get infected so they can infect you all.
Method for getting away is; When your SP is up. Sprint with knife and make a lot of turns. Then when it's on about 1/4, take out gun and keep sprinting. Quickly turn around and shoot all zombies for about 1 sec. Go back to sprinting. Repeat