In the map Crook's Hollow, you will meet your first task where you should avoid combat by all means. Now, doing the mission by the means it is supposed to be played, you have to find the boathouse key in the shack with the breakable wooden frame on the right side of map, then bring that key to the boathouse on the left and continue on...however, there is a really good weapon hidden behind all those robots that are behind the shack that holds the keycard. There are a few guides on how to do this with silent kills and 4-5 bottles, but you only really need 2 bottles, and some trial and error. Make sure you have multiple save files ready tin case of failing and not doing this right. Keep at least a few ready in case you mess a step up (which will happen for sure, took me around 20 tries to perfect it).

Also, MAKE SURE YOU HAVE 2 BOTTLES WITH YOU FOR DISTRACTION. They are a must (if you don't have them, fast travel to the vendor is only one click away).

You should do all the steps mentioned below while crouching, but that should be logical by now.

So here is how to do it step by step:

1. Keep Jade far from the group, I left her on the mud road that goes down towards the first robots when entering the level. This is very important for the last part.
2.Take Diggs and Elvis to the shack with the breakable wooden frame on the right of the map, making both of them stand right next to the blockade. Be ready to do a few things at once here, WITHOUT using ambush mode. While in real-time, use Diggs to break open the blockade leading towards the shack, and immediately hide him in the bush that is next to the shack. Right after that, use Elvis to sneak inside and get the boathouse key. By doing that, the warden that is trying to figure out what is going on is just around the corner, giving you time to move on. Immediately leave the shack from the back where there is a giant opening, and head towards the second white object in front of you (in the middle of the next area). DO NOT cross the orange/red markers on the ground, those are going to end your try. Because of this, stand next to the one of those tiles that is not orange/red, but is closest to the second white object. There should be only 3 of those tiles in front of you. While doing this, the warden will be coming back, so you only have a few seconds to do this. Because of this, save when you have found the perfect spot and be ready for the next move.
3. After you saved, go towards the second white object. You will slowly start to get spotted, but there is a small window where you can bypass this by using the *hidden* mechanic in the game. The bots WILL NOT SPOT YOU IF YOU ARE HIDDEN, NO MATTER HOW CLOSE YOU ARE TO THEM. This is the reason why this is possible. So, head towards that second white object, and spam the hide key (right mouse click by default). You will be able to do this just barely, and you will successfully hide next to the white object. Don't get frustrated if you fail, I failed more than 10 times while trying to figure this out. After you successfully do it, save.
4. Now, you can move from one hidden spot to another by releasing the hide button, and spamming it again while slowly approaching the next tile. Use this tactic until you reach the location when you are very close to the Trooper bot overlooking the chest. Save again when successful.
5. Be careful now, even bots have sensors around them, so you cannot just stalk behind them. Do not move too close to the trooper bot, or you will be spotted even faster. Now, you will need to do the same thing you did when you approached the white object before, just now, you will have to move next to the wooden boat in front. Same thing, save and try until you make it. You should understand how it works by now.
6. Now, use that one-by-one tile technique you did with the white object with the boat, until you reach the last two tile that are facing away from the bots (where Elvis is in the post picture). When you do this, save, and prepare the ambush mode. Use one bottle to distract the trooper, to the point he is facing the wreck (again, see pic), and use the second bottle to distract the warden, making it turn 180° towards the other two bots (another trooper, and speaker, see pic). After you do this, use one action to move Elvis towards the create with the weapon chest. You should have no more orange/red tiles next to the weapon chest. Exit ambush mode. Now, you can open the chest no problem.
7. But now, how do you get back? Well, it is very easy. Remember Jade and where we left her, all the way back on that mud road? Just switch to Jade and use the re-group all key (hold space by default), and all your characters will teleport to Jade.

Congratulations, you just got an excellent shotgun much earlier than you should!

Enjoy!