I thought I'd give some quick tips for this. So VORON Station is one of co-op only Briggs missions. It's quite long, especially on perfectionist, so you aren't going to want to do this twice for both partners to get the achievement. The way to earn this achievement is at the very end of the mission. Briggs and Sam must place C4 on a wall to get inside a room with two people. One of these people is the mission target. Briggs will grab one, and Sam the other. Here is where the achievement begins.
In a minigame fashion, Briggs and Sam have to do a facial scan on both people to determine which is the target.
This mini game consists of a circle scanner being moved with the right stick. The targets will struggle making it difficult to lock the red scanner on their faces. When it is locked the circle will change from RED to GREEN.
If it becomes to difficult to lock on, tap X to smack the target, calming him down for a while.
Whoever completes the facial scan first will be awarded the achievement. No matter who completes the scan first, Briggs will always have the target. Now...
During the following cutscene, the person who did not get the achievement will be taken hostage by their target. DO NOT KILL THE HOSTAGE TAKER. THE MISSION WILL END.
Just wait for Briggs or Sam to be shot... The game will restart directly before the C4 blast. Now the second partner able to get the achievement.
This can be done in split-screen, and although difficult, could be done by one person with one controller.
It is very easy to get or work on other achievements during VORON Station, such as Tactical Style achievements and other co-op achievements.
Hope this helps!