The action takes place in the bus depot that you moved through later in the stage, and has a number of long, winding evacuation corridors (watch out for Charger s!) that lead to a scaffold platform where the switch to begin this fight is located. In front of the platform is an area of tarmac, but the bus depot itself is closed.
The long, narrow, mesh-fenced corridors (1) are where most Survivors go to die, as it’s incredibly difficult to keep the masses of Infected from attacking from all directions, and there’s little strafing room. A better plan is to use the ladder and have all teammates head up to the scaffold platform (2), after dropping Fuel Cans or waiting to lob Molotovs to burn the Horde that mainly swarms around the entrance near the ladders.
You each take a side, look down from the platform, and blast away. When the situation becomes dire, drop to the tarmac below in the larger area where the body bags are laid out. Then run to the ladder during a lull, or after throwing a Bile Bomb or a Pipe Bomb, and ascend again.