The first finale we tried was No Mercy. We could make it to the hospital roof with few problems but once we called the chopper in, it was just a matter of time. We tried running around, making a stand, hiding on roofs, hiding under ramps. Every time, without fail, we were slaughtered. All we ended up proving was that we couldn't play Left 4 Dead.
If you load up the finale on No Mercy, you can see the room for yourself. Get to the roof of the first building and look across the alley. See the doorway on the small building with the satellite dish? That's the entry to the Jesus Room, accessible only once the rescue vehicle had been called, opened by three players frantically meleeing the sealed doorway. Once inside we were free from zombie attacks and waited until the chopper arrived. When the rescue vehicle called for us, the weak and wounded broke left, acting as bait for the hordes while the healthy broke right, throwing a pipe bomb for good measure. Amazingly enough it worked. Because one of us survived, as far as the achievement was concerned, we all did.
With that, our Friday nights for the foreseeable future were set. Valve may not be the fastest developer on the block, but their record of software support told us that the lobby glitch had a limited lifespan and once it was gone, our hopes of getting the achievement were gone with it. We consulted Valve forums for word of when a patch would be delivered. "Soon" was all we found. We researched Xbox Live certification processes, working through how long we'd have once the patch was handed off for certification. During the week we read forum threads, watched YouTube videos - anything to give ourselves a greater chance of success for the coming Friday night.
For Death Toll there was no Jesus Room, but there was a Jesus Rock that you could climb atop. As long as you picked off smokers trying to attack from the water, the zombies couldn't get you. Well, until that one tank crowd-surfed the zombies up onto the rock and took half of us out with one hit. Even with that, we still managed to finish the finale.
For Dead Air there weren't any rooms to hide in, making the roof of the plane the most obvious yet inaccessible choice for survival. Once again, Petey came through, finding a bug that allowed you to propel yourself on to the roof of the plane by meleeing a chaingun to "wind it up," then jumping on it. Once on the plane, the only real threat was smokers, but yet another bug offered immunity to their attack provided someone was constantly meleeing you. And so we survived Dead Air, four of us crouched on top of an airplane, meleeing each other in the face until the plane was fueled up and ready.
We had left Blood Harvest for last because there were no easy fixes for this campaign. No rooms to hide in or rocks to climb on. We hoped that in the weeks spent completing the other finales, an easy solution would arise, but no joy. To make things worse, Valve had announced that the patch was coming.