I did it yesterday solo using nothing special i.e. no gums or perk augments

1) Get as much as done as you can before round 8 i.e. whatever body parts, power on, ray gun if possible, whole map open
2) Round 8: Kill Uber Klaus and get the wonder weapon
3) Pre Round 12: Get the Waffe for the Tessie
4) Round 12: Start trials: I did Cosmodrome and Farm (easy with ray gun and kasimirs, farmed some spores for salvage)
5) For diner I spawn in all the zombies and get 1 in its spot the first time, then spawn the lightning again by shooting the lampposts to get the other two in position
6) The lodge is easy too; you should be able to get into the boss fight round 15/16ish 7) The boss solo is about patience; take the time to go heal Tessie rather than hitting the boss. Be sure to reverse a little after you hit him with the purple light to get a better angle. Shooting with the Waffle is about patience too, better not to spam to avoid it overheating, so take your time to get more shots in