Specialist: Sharky Boshaw
Head to the marked location in Chateau Boshaw and talk to him to start the mission. Followers with good firepower like Hurk, Gina, or Carmina will help in this mission.
First, you have to arm five traps surrounding the facility. These are pressure plates along the metal walkways. After arming the traps, head back to the facility to turn on the pressure valve.
After that, talk to Sharky. He’ll ask you to drink with him, with the “party liquor” on the table. Drink it and you’ll wake up in the evening, with a large number of highwaymen already ready to attack.
Head to Sharky’s Tower and go to the marked position. You have to defend the western side of the facility first. Use the mounted machine gun to mow down the enemies. Sharky will help by throwing explosive barrels at the enemies. Make sure to shoot those when there are enemies and vehicles near them. Multiple barrels near each other can cause a chain reaction.
Take note of the enemy positions; the high-pressure pipes are exposed and enemies will always try to get near to shoot it. Keep mowing down enemies on this side until Sharky tells you to defend the other side this time.
Like before, you get to use the machine gun. You can also order your ally to take position behind the cover in front of the high-pressure pipe. If you have access to proximity mines, it will help placing some near your position, especially going to the guns.
Later on enemies may overrun your position and some will be able to sneak inside. The enemies in the eastern side will also deploy smoke screens so use the tracers from their guns to pinpoint their location. If the attack seems to ease up but Sharky still doesn’t update the objective, that means there’s still an enemy lurking in the shadows. This happens when the game’s AI acts up and fails to attack. If that’s the case you have to manually search for them and kill them. Just make sure to return to the facility immediately.
For the last wave, the enemies will be attacking both sides at the same time. If that’s the case, order your companion to take position on one side while you handle the opposite site. Reinforcements will have a MG truck on the western side while the eastern side will have paradrop support. Just kill all enemies as fast as you can until all of them are dead. Once the last enemy falls, the mission is complete.
We have questions and answers related to this topic which may also help you: