When going for this I would suggest you either beat the game once or start the area once your over level 30, as the waves go on the zombies levels will increase and you will find yourself overwhelmed if your not a high enough level to take them down, so I recommend leaving area for last while going for the achievements or find a coop partner who is over level 30 to help you.
You'll be doing this in Arena A (easy)
When doing waves 1-30 , you and you're coop partner/s will camp it out in the area on this clip, while being in this small area by the work beach the zombies only spawn on the centre path in the middle of the bridge and the right side. This gives you a great advantage as you can have one guy killing the zombies on the centre path and the other cover the right side, don't go too far to the left as that will spawn them on that side and then you'll find yourself overwhelmed.
Also as much as it is tempting don't stand on the bridge or close to it, Thugs and infected can knock you off the side. Even when your not on the bridge if an infected comes up behind you when your standing close he can push you off.
That being said your going to need these to get you through the arena:
MEDKITS ( Lots and lots! Posssibely more then 30 Meds)
MONEY (Money is key! Your weapons will become damaged and will need repairs from time to time)
GOOD EFFECTIVE WEAPONS (I would go with sharp weapons like a Machete or a Katina, that way you'll have a long swing so you won't have to get too close to the zombies, less chance of losing health)
Going in the arena with 2 guys with the right equipment and the right level should be doable, 3 or 4 is better but make sure you communicate and stay in a tight formation, playing any zombie game you'll know going off alone is never a good idea!
Zombies are pretty easy to kill for the first 10 waves, each few waves will increase the level of the zombies and every wave has more of them and they will come at you in groups so be careful for the suiciders as being too close to one of them can down you instantly. These and Infected are the ones to watch out for! In the later stages you'll come across infected that are on fire and even when they are dead the fiery copse can still damage you.
Make sure that you are fully healed after every wave and make sure you keep an eye on your weapon durability as it Won't really do any damage if the weapon is near broken. Visit the work bench to repair after a few waves. Loot the corpses after a wave is done, you'll find money, health and sometimes even ammo.
Guns help too to kill suiciders in the later wave their will be lots of them and killing them from far away with a gun is better then having them get the jump on you, But there are other methods of killing them, you can walk up to them until you see they are about to explode and jump back or you can jump and kick them too the ground.
Clips will give you an example of taking them on close and long range, both effective:
Wave 1: Walkers
Wave 4: Infected
Wave 6: Toxic walkers (These ones can blind your vision and damage you from toxic effect)
Wave 7: Suiciders
Wave 9: Toxic Infected and Floater
Wave 11: Fire infected( Do increased damage to you as they are on fire and can still damage you with the fire after they have been killed)
Wave 16: Butcher
Many thanks to Internal Decay and xCEL7IC ZOMBIEx for joining me in the arena.
Any questions about the game or solution, please let me know.