Gabe Chauvin
This is one of the cooks that you can easily kill. Just take out the enemy outside then lure the sentry or the other guy inside so you can ambush them then finally take out the target himself.
“Beaks” Brunner
This is quite an easy kill as well. Head to location and sneak behind the shacks. You can actually open the backdoor of one of the shacks so you can stealth kill the sentry. Work your way to the shack where the cook is located; you can actually shoot him from the window. With the sentry and target dead, it’s up to you to clean the place up or leave it as is.
Lonnie Grima
He is located along with some armed men in a garage-turned lab. You can approach stealthily then throw a grenade from the doorway to kill him instantly. Be warned however that the nearby sentry may call in reinforcements. It will be hard to perform stealth kills without alarming most of the hostiles but just in case, there’s an empty building that you can enter and use it to ambush enemies from the stairs.