First of all, you are going to need a brick for this, as soon as you unlock this weapon it can randomly spawn in weapon locations.
Next is what chapter to do this on. I personally found the fifth chapter "Full House" to be easiest to do this, but this may vary for you. You have to restart the level until a brick spawns in one of the four weapon locations on the first floor. As soon as it spawns I cleared the first floor, picked up the brick and proceeded to the second floor, that way you don't have to restart for the brick again.
So on that second floor you throw your brick in front of you (don't throw it behind the invisible barrier in the spawn room!) and afterwards punch out the first guy, grab his weapon and throw that weapon in the corner of the spawn room, that way the enemies can't get to them anymore.
I proceeded to disarm the second and third guy, at that point you could try to go for the achievement, but I found it really inconsistent with three, so I disarmed the 4 guys in the upper right room as well by luring them to the previous room and hitting them either with fists or the door and instantly grabbing their weapons and throwing them into the spawn room.
If an enemy grabs a weapon, don't hesitate to run back to the spawn and lure them to you, or just try to get them on the corner.
The disarmed enemies move pretty weird, so it takes some time to get them in a line, but with four guys I got it on my first try after moving them together. And if you don't get it, just die to try it again.