How do I complete the 'The Madness Contained' achievement?

The Demon Hunter class achievement The Madness Contained requires you to "Spend 150 Hatred and 50 Discipline in 6 seconds."

Using the Vengeance passive ability, it's simple enough to get 150 Hatred and Preparation can instantly restore all Discipline and with the Invigoration Rune can add 10. Using a 14 discipline skill twice, Preparation with Invigoration and that same skill thrice more with a +2 discipline item equipped or fast Discipline regeneration or using the passive Perfectionist to bring he cost down to 12.6, would consume 50 discipline. Hatred is easy to burn in no time with 3 Cluster Arrows. There are many other examples where the math will work out to count up the costs.

The problem I'm having is the cooldowns are too long and/or the skill costs too low to do this in 6 seconds for Discipline skills. I feel like I'm missing something simple or I'm doing it wrong or maybe I'm just not good enough. In theory, if you had +20 discipline, you wouldn't need preparation and could just spam companion 5 times, but I've yet to see anything with that much of a Discipline boost.

In what order should I use which skills in order to complete this achievement?

There is no need for +discipline gear. I got it with Vengeance in my passive slot, then using smoke screen/shadow power, smoke screen/shadow power, preparation, cluster bomb x3, smoke screen/shadow power, smoke screen/shadow power,.

Also, it seems that you can't get the achievement while in town.

EDIT: Just got in Bastion's Keep using this method so can be done there. (patch 1.04)

Equip vengeance passive skill to attain 150 hatred. Equip (3) +6 discipline items to attain 48 discipline. Equip preparation with punishment rune (spend 25 discipline to restore all hatred, no cooldown on preparation). Cast preparation --> cluster arrow --> cluster arrow --> cluster arrow --> preparation in that order.

The easiest way to to this is Vengeance (passive), Shadow Power, Vanish, Preparation (with + Discipline rune), Cluster arrow. Cast Vanish first, Shadow Power second, Preparation third, Shadow Power fourth, Vanish (again) fifth, then shoot Cluster Arrows three times.

If you use a fast 1-handed bow and spam the spells fast, it is easy to get. Vanish is cast first because it has a longer cool down. By the time you cast it again the cool down will have already been up.