First, get enough points to open all the doors to the power and turn it on.

When you get enough points, get Bouncing Betty's and Juggernaut. Try to get good guns (mainly the ray gun, Wunderwaffle, and most of all the flame thrower).

After that save up your points for a few rounds. Get enough to upgrade the flamethrower.

After that use your downgraded gun and get enough points to open the door to go to the cat walk (quick revive).

Have one person go into the tunnel and go all the way to the back. Have another person go by quick revive, and turn around. Have him go by the top of the tunnel and turn right.

You will see a pillar on the wall. Have him walk into it and crouch. He needs to look at the barrier by quick revive (this is the only barrier that you guys need to look at) any zombies that come through there - kill them all.

The person that is in the tunnel (as if you're walking into the tunnel) stand all the way to the left of it. The person in the tunnel should have an upgraded flamethrower.

When the zombies all gather up by the bowie knife, use the upgraded flamethrower and burn them!

This will get you many many points. Try to get monkeys and use them if you need it.

The person on the top of the tunnel should not have a ray gun, because when you shoot, it pushes you back. You will get out of the glitch.

The person on top should have an Upgraded shotgun like the Upgraded Trench.