User blog comment:GamerPr1ncess/CoD: WAW/@comment-1525226-20100503175543

This got me 32 with two people:

Around round 3-4, go Left through Animal Testing. Then open up Z-C (Catwalk area). Unlock all doors accept the first door to the right when you start. Then all players camp by the Catwalk Mystery Box Spawn. Two at the front crouch, two at the back stand. It works well.