Hey guys before you read the steps please don't copy this. But I do need someone to actually record it. This glitch isn't that useful but it's very decent for racking up a lot of head shots. This glitch was found by me and if you can make a video and give me credit that would be ok.

Steps:

1) Find ladder to get on top of the bus (can be found in one of the storage rooms or the 1st turbine door)
2) After attaching ladder on bus go about halfway up on it and stay still.
3) The zombies should break in and pile up on the window and walking towards you.
4) You and your friends can take turns doing this (like every stop or something)
5) Your friend should stay in the corner thats next to the robot.

I know this glitch isn't very useful but you get the zombies heads mainly. I tried this out and it works so go try it out

HAVE FUN