Video Guide
Mission 2 Dead DropMake sure to bring weapons with no scopes to work on iron sight achievements. Load up mission 2 on the easiest difficulty and sneak into the fortress near the back of the map. There should be seven enemies in this area as well as a truck with one driver. We want to quietly knock all of these enemies unconscious with our melee attack. Then pick up their bodies and pile them together in one of the rooms, making sure to create a manual save at this point.
From here we can start grinding pistol masteries and achievements for ghost kills, secondary masteries and achievements, we can also chuck a grenade at them for trap kills (and a triple kill with one grenade for an achievement), pick up any of the weapons they dropped and use those for found weapon kills, and there is even a heavy gun on the box in the courtyard we can use to grind out heavy gun kills. Every time we eliminate the group of enemies we can just reload our save and go again as all of this counts even if we don’t finish the mission.
We can grind out the following achievements here: