Barrier cheat: After you go down the first elevator, you have a set of dual stairs in front of you with a barrier blocking it. If done correctly, you can strafe jump over it. If you make it over, go down and turn on the power and activate all 4 DEFCON switches. This will get you into the pack a punch room, but the door to the warroom will be closed so your team only has to sefend the 2 windows in the PaP room.

Strategy solo: Go down the elevator, get to the lower section of the war room (where juggernogg is, that level). Open the barriers at either end of the room. One is under the steps that you came down, the other at the opposite end.

I suggest getting the power on and getting Juggernogg, but you can do it carefully without juggernogg.

Now, just slowly walk a circle around that lower section of the war room, dodging zombies as needed.

The Winter's Howl (winter's Fury when PaP'd) is like the new wunderwaffle, get it if you can.

I made it to 29 solo and I am sure I can get further.

Note: The trap in the Speed Cola hallway s missing a piece. It is located in the War Room, to the right of the freight elevator. Get it and go to the upstairs trap and hold X to repair it.