Originally posted by .
You dont need trophys like this in co-op this can be easly done IN single player as i have...the reall Co-Op trophy expolit is to focus on... Genocide Master....*and all inbetween*
You can use if you have a Co-Op partner who doesn't mind doing nothing for several hours. If your partner hosts a Co-Op game, as the guest your kill count will be persistent between sessions, meaning that if your host saves at 10:00 at 9/28 you kill a few thousand zombies, when the host reloads the save the time will be 10:00 again, but you will still have all your kills. A modification to this strategy that I'd suggest is to have your host carry the multiple bike/driving magazines, since the guest's inventory will empty out every time the game is reloaded. The host can drop them all for the guest right at the start, then the guest will continue his rampage. Be aware however that if you get disconnected, or either you or the host quits, you will lose all progress and have to start again at zero.
this is NOT your method & you did not give credit. This is from ps3trophies.org