First thing is to equip everyone in your current squad with a shotgun.

Next you wanna choose maps with enclosed space like the following ones, which give you advantage in utilizing your shotguns.

Play in bomb defusal mode on said maps, difficulty set to Normal or Hard, and watch kill count rises.
Eventually, after 15 to 20 rounds, the three delicious achievements are in your hand.

Try using the suppression skill when equipped with a shotgun.