Only glitch I know is: starting at the Mainframe,Player 1, the door that opens up towards Teleporter B. Stand as if you were looking straight at it, tuck your self into the left hand corner of that door (DO NOT OPEN IT!) Player 2 needs to be on the other side of the door, you will need the power on so you can run all the way over to the other side. Now Player 2 stand facing that door Player 1 is at, and go the left side, tucking yourself into that corner. Do not move from that position. Zombies will not touch you, they will all walk over to the other door going towards Teleporter A.
Now in Player 2s position your only problem will be the window directly in front of you, because zombies will attack you once through the window. This glitch is best used when both players have 2 PAP weapons and betties, and ofcourse having Speed Cola and Juggernog doesn't hurt either. When zombies are huddled around in a circle by that other door, chuck grenades and monkeys to get lots of points. It's very useful if Player 1 has a PAP Wunderwaffe.
Aside from Player 2s problem with the zombies coming in from that window, the Hellhounds are not affected by this glitch.
This glitch also works with 4 people. But only 2 are needed to stand at the doors.
That's all I have, if you already knew this, well sorry I couldn't help you.