You will need 2 controllers do to this.
1. Wait at the screen where it says public match.
2. Press X on controller 1 to bring yourself into the lobby.
3. Back out using controller 1 all the way and leave and disband party till you get to the main screen.
4. Press X on controller 2 wait till error message pops up then press X on controller 2.
5. Press X on controller 1 twice.
6. Press X on controller 2 once then after 1 second press again.
7. Don't press anything.
8. When says connecting to online service spam X on controller 1 then message should go and come back again carry on spamming till it says public match.
9. Should duplicate then go into a game and get a kill.
10. Might crash app start up again if not saved do again.