If you have four players this will work out great.

Open all the dors to the stage and turn the power on.

Then there will be the stupid crawlers. Link the teleporter and go upgrade your guns (don't leave your teammates behind).

Upgrade all guns and go to the alleyway, but use the doors by where you turn on the power.

Go into the alley have one person cover the window but never open the door. This will keep you going to round 52 if you're good.