In the lobby with the menu glitch on the second controller:
1. Wait for the game start counter
2. At second 8 start media player with controller 1.
3. Wait for 50 seconds in it.
4. Go back to black ops 3
5. Select map, change gamemode with controller 2
6. Back out controller 2 (or hold home button and log out from ps4 with controller 2)
7. Wait for the game start and your friends and randoms can join your custom game lobby.
Hope it help some people