Essentially max research fireworks and equip these augments. I do directors mode, Astra round 14 gives you 41-42 zombies a round. DO NOT ROTATE THE BUSTS if you do Oscar spawn every round and it gets annoying. Train your 40 zombies shoot and activate fireworks, they scatter in the ground and lead your train through them and you get 30-40 firework kills every time.
*THIS ALSO COUNTS TOWARDS YOUR 300 PAP AND ARMORED.
You can change short fuse to high yield if you’d like!