1. Safe Barricading
The simple but effective way of creating a barrier is to move boxes found scattered around the map to create barricades from the zombies entering a certain room. Moving boxes around can be very useful if placed in a sturdy barrier.
2. Running and Gunning
While you have the potato gun is can be very useful to knock back zombies, but it will deduct a few points every shot! Be wise.
Shotguns can be used to slip through walls. Allowing some to enter others barricade room.
3. Bush hiding
A short and small weapon like a stick, drumstick, glock, or uzi would work, to shoot or bat away zombies that get too close, and not showing themselves to zombies.