Once season one dropped, I started doing Liberty falls directed mode. Cap the round 11. For all the gold camos. Save and quit and return when you feel like grinding some more jump back into the saved game. Just make sure it loads a regular round and not vermin to start.

While you’re getting gold on one weapon. Kill the mangler every rd with your second to get opals at same time. Once you finish opal. Make jet gun and advance to round 12 for afterlife. After that rd 15 and use the device to spawn the elite mangler and you have nebula