Dogs only won't have special rounds and no idea on the dogs spawning slow, I know with mini-bosses like Brutus I have changed the health and damage multiplier to half and it slowed the speed of them but not the spawning frequency. Make sure your spawn frequency is on quadruple.
Make sure you aren't kicking anymore, have the person joining from multiplayer disconnect then reconnect their controller. Allows you to be able to do several attempts a lot faster.
Depends on the map, on BOTD you need miniboss, zombies, and vermin. I would just leave all of them enabled, but on Voyage it helps to increase the spawn rate of catalysts.
Founder: TripzHD
Prerequisites: 2 players in a voice party
Tutorial:
Step 1: Player 1 needs to go to multiplayer, then click custom games, then hover over options WITH THE D-PAD.
Step 2: Player 2 needs to be waiting in a custom mutations game in zombies.
Step 3: Player 1 needs to join player 2...
100% patched with this method, even if you get the screen to stick it kicks player 2 out of the game before going into private match. Hopefully another method will be found.
Better way.. kill yourself as non-infected with a good gun next to a wall then come back as infected, stand next to it and throw the tomahawk at the wall then right after hold square. It will take a few tries but if you do it next to a wall you can do it fast.
For the love of god don't do this with the kill 200 zombies with a gun pack a punched in the machine challenge, you HAVE to pack a punch it in the machine no gums and I just wasted 3 hours doing that and accidentally finished the challenge.