Kane & Lynch 2: Dog Days

Load up chapter 1. Make sure the difficulty is set on easy. Playthrough the chapter; once you've run through the mini-mall, you'll come to an outdoor market where 2 cars will pull up and about 8 men will get out and shoot at you.

Run over and stand somewhat close to them. Most of them will be in cover, so they won't bombard you with bullets and kill you. Once you're down, kill 5 of them. Also it helps to have the mac10 looking gun with full ammo. This makes it easier to just spray and pray.

I just got it pretty easy.
On 'A thousand Cuts' there will be a a cutscene in a TV-Shop, where Lynch whines about Xiu. After that scene u will be going through a restaurant passage fighting some cops and a dog. When u proceed further through the restaurant all remaining cops will back out. Now look at the pillar in front of the exit. There should be a fire-extinguisher. Pick it up and throw it on the ground a bit out of the exit. When u get near the exit u initiate a horde of swat-guys spawning and trying to storm the door. Just stay in the doorway and let yourself get downed. Now shoot the fire-extinguisher and the achievement should be yours. If it doesn't work on first try u can reload the checkpoint and start right before u get to the fire-extinguisher.

I did this on the next to last level on easy, It's the level were the helicopters are crashed into the skyscraper. I highly recommend having the shotgun for this. Its makes life alot easier. 1 shot 1 kill. I think i had like 9 kills while down with the auto shotgun on this level.

This can be done in Blood, Sweat & Tears. Play until the game suggests that you grab an enemy from behind and use them as a human shield while they're not looking. The enemy will be in another room facing away from you and positioned next to the door into the room. Kill him and head straight upstairs. Let yourself be downed upstairs.

Play on easy so you can resist more damage while downed. Use your pistol to make head shots on the enemies. There's lots of cover. Try not to get stuck in a narrow space where you can't turn. If you do, just wait for enemies to pop up into your view or reload the checkpoint. You can reload the checkpoint any time if you fail and want to start over. Now just take cover and kill five enemies. There's a little more than five upstairs. Kane comes up quickly to provide support.

Tip for Down But Not Dead mode aiming:

When you're looking at your intended target with your body sideways or your head facing them, you can aim well vertically and horizontally, while shooting backwards limits vertical aiming.

i just get it on the underground parking lot protecting glazer....
just grab a extinguisher, throw it to stunt and run kamikaze, you fall to the ground and kill the police thru the door....obviously you wull the shotgun....and set the game on easy...