Okay, when you get 3,000 go upstairs, open the cabinet to get the flamethrower and go next to the stairs, there is a little funnel place where they can only come at you from the front, keep clicking the move stick to shoot like a normal gun, don't hold it down. This shoots it farther and it kills them fast. Erm... Yeah, that's it. I got to 15 on single player like that. When you think its the last zombie of a swarm, toss a grenade so it loses its legs and you can go repair everything while its pulls itself after you. I don't know, that's mine, it's only gotten me to 15... Now, you must know that I have Attention Deficit Disorder and I get bored easily, after 15 I decided that I wanted to see a zombie up close so I ran right up to it to see its face, so I'm positive it could get you guys father.