Go on the parish on survival. On the bus depot grab a bile bomb and start the alarm (this works on 2 player too).

Go to the mail boxes across from where the bile bomb is. Jump on the mail boxes and throw the bile bomb next to the porta potties.

When lots of infected are around it jump on them, then jump on the porta potties. Then jump on the top of the thing that goes across in front of the porta potties (next to the fence to the outside). Jump on that thing then jump over the fence.

Run to the saferoom (watch out for SI, if you get caught by them you are screwed). Wait for your teammates to die and you'll pass the level.

You'll then be on the next level in the parish. Go through the sewer and you'll see car alarms everywhere. Do not shoot the car alarms or survival will start. So avoid the car alarms and get to the cemetery saferoom.

You'll get to the next level (the quarter), but you'll have to kill yourself first to get to the next level.

Go to the restaurant where the stairs are. Go to the top of the stair case, crouch then jump to the bottom. Don't jump on the table because you won't take damage (it causes 6 damage every time you jump off to the ground).

When you're uncapped wait until you die. When you die you'll be at the parade float and it'll be like survival.

Note: you'll have to do this again if you want to play the map again.