This achievement may seem to be hard but it isn't as hard as you think.
1. Firstly you want to have 4 players, probably can be done with 2-3 but having 4 makes it a lot easier and communication is VITAL.
2. Load up the Kino map and have each one of you stand at one of the 4 windows.
3. Assign one player to be getting all the guns - should have 2 in the first room.
4. The rest of the players must try and not be selfish as their job is to open the doors for the main player to buy all the guns. The only guns that the other players should buy are the stakeout and claymores and maybe a cheapish machine gun.
5. I always stayed in this first room until stage 5 started.
6. Once stage 5 starts, run to open the one at the top of the stairs and then get the main player to buy their third gun to the left as you go through the first door.
7.The other players should have enough to run through and open the next door into the room with the double staircase which holds the Stakeout and the MP40.
8. Have the main player buy these 2 weapons... and again assign yourselves to windows... if there are 4 of you, I would suggest having 2 players at the bottom windows and 2 around the stairs area... However, the main player buying all the weapons should stay at the top of the stairs as most zombies will come from here and therefore they will accumulate a large amount of points meaning less waves needed to get the achievement.
9. By round 7/8 I would suggest people opening the next 2 doors, there is one gun in the next room - the MP5k... buy that and straight away have someone open the next door into the Theatre.
10. DO NOT TURN THE POWER ON.
11. There are 2 weapons (M16, Claymore) in this room, I always got everyone to buy the claymores as they are very useful and replenish every round.
12. Camp around in this room and have the main player have between 7-8 thousand xp.
13. Once the main player has enough, create a crawler by throwing a grenade and blowing the legs off.
14. Now be quick, get the other players to open the remaning doors but DO NOT TURN THE POWER ON YET!
15. There should be no weapons until you get outside, then open the next door into the room which is to the left of where you begin on this map.
16. If someone has enough money to open the final door making a circle of the whole map, open it and stand near the teleporter bridge. (Circle on floor)
17. have another person run back with the main player and turn the power on.
18. Once the power is on, the main player needs to run and buy the bowie knife which is found under the balcony next to the jugganaut machine. (3000 xp)
19. Run and use the teleporter, you should have at etleast 750 xp left...
20. Buy the frag grenades on the wall and the achievement should pop...
-In total you need around 13,500 xp.
-The more zombies the main player can kill the better.
-Stakeout and Claymores are a good combination with an automatic gun for when 2x multiplyers are obtained. I always kept the stakeout as it is a good gun until around round 11.
-You shouldn't need to get much further than round 9 or 10 otherwise it gets too hard.
I probably haven't worded this the best in the world but if you need more help just send me a message on xbox live and i'll talk to you.