How to Survive: Storm Warning Edition

I found a large group of Zombies with helmets and armor near the boat to Santa Barbara on Los Riscos Island.
They where feasting on a cadaver there.

I used my Golden Iron Axe and the number of zombies increase your chance to get Instant kill. Be ready to hit when it lights up.

I only charged my axe the first time to knock some helmets off, the rest I only managed to charge for a second and sometimes no charge at all.

an instant kill is when you see and push after stunning zombie with an attack.

the easiest, hassle-free way to get this achievement is on Los Riscos island shortly after starting the game.

best weapon to use is the rusty machete.

kite zombies around until you have at least 5. You don't need to do anything fancy, a quick hit with the machete will give you the prompt almost every time.

LATE GAME:

Los Riscos is still the best place. Normal unarmored zombies still spawn in the spots you traveled early game, but so will animals and exploding zombies making the kiting method difficult.

Late game, best place to get Wait Your Turn is the very place you start the game (bottom center of Los Riscos). A horde of zombies will be feasting on a corpse there. Make sure to get there using the path from the east (right) side of the island. Most if not all will spawn unarmored if you approach from the east side of the island. Coming from the west, @ half will spawn with armor.

best weapon to use is still rusty machete. Again, nothing fancy. One quick hit against an unarmored zombie will almost always yield an prompt.

make sure you're well armored and have a healing item at the ready if needed.

Walk into the crowd pushing and getting the few s that appear. Repeat until the achievement unlocks.

This zombie horde is also the spot to use if you want the # of kills within # seconds achievements.

One of the first oppertunities to earn this achievement is when you have to get a jerrycan full of gasoline for Ramon. After opening the door to the gasoline, a large group of zombies ambushes you and you can get the needed instant kills within this time limit.

Update 29-01-2016: Fixed some typos.