Well, everything is smooth and pretty easy up to the 52nd kerotan. After that, the hell starts.
Therefore, I'm gonna add few details on each kerotan found after the 52nd.
After beating up volgin in a fist-fight, make sure to save after EACH section you shot the kerotan in. for Example, when you shoot the kerotan Groznyj Grad Escape, don't save right away, wait until you finish this section because if you did and died or restarted, it will bring you back from the beginning of this section, not where you saved.
Shooting the kerotan as you know will make a voice that you'll hear, even if you're on the motorcycle and it's too far from you, which means if you feel like you shot it but you didn't hear the voice, so if it happened and missed the kerotan, just hold RB,RT,LB,RB, Back & Start and it will bring you back to the title screen which you can reload the last save point.
Just to be on the safe side, make sure to shoot the kerotan AGAIN if you died or failed during a section.
53 & 54: these kerotans you'll be able to shoot easily since Eva will stop so you could shoot the enemies.
55: the kerotan will be on the left side of the runaway. to make things easier on you, only shoot the passengers on the bikes following you, and let the drivers follow you. This will prevent more bikers from spawning and ruining your attempt.
56: on the Right side of the runaway, use the same tactics mentioned for 55.
57: Just make sure your setting not in a prone position to be able to visualize the kerotan.
59: In this section, you'll be encountered by an ambush, where Eva says "it's an ambush", pay attention cuz the roadblock where the kerotan is lying under is coming next.
60: will be on the right side of the road, look at 1 or 2 o'clock setting in front of a rock on the floor at the beginning of this section. You can easily shoot it using a machine gun like I did (I used the patriot)
61: will be on the left side of the road at 11o'clock on a rock after a small downslope. I used the SVD with it.
Lastly, the achievement will pop right after you shoot the last kerotan, meaning that you don't have to wait to beat the game and get the right rank.
Hope these info helped and good luck to everyone attempting this <:+)