- When you fight off the infected in the cabin, make every shot count. If you miss once, better restart unless you're already pretty far in the encounter. In that case it's not so bad if you wasted one bullet.
- Do not pick up any ammo until David starts pushing the object in front of a window. If you don't pick up any ammo, David will give you 5 or 6 shells before moving the furniture. Once you have that, you can pick up the ammo that was dropped by enemies (about 2 rounds I think). If you pick up the ammo mid-battle, David won't give you free ammo, or less of it.
- Use the bow on infected that are already inside because you can retrieve the arrows, use the rifle only if it gets too crowded and on clickers
- In the area where you sneak around infected, go immediately to the right and you can crouch through a hole in the wall. There's some explosive material here. Now go back, and there should be a clicker waiting around the corner here. Sneak past him and drop down into the hole. Behind you there is a bunch of crafting materials. From here you can easily reach david by headshotting the single clicker in the area and climbing the ladder
- When you're on the catwalk, brick+knife the clicker and grab all the supplies from the room he was " guarding" (or lure him into the catwalk maze and sneak past him)
These materials + everything you can collect in the bloater room should be enough to craft a total of two molotovs and two nail bombs. I don't know if I missed a material in this guide though, as I came up one blade short in my second playthrough. Maybe you can consult a real walkthrough to see if I missed anything.
My strategy for the fight was the following:
- Hide against the stairs until the first runner appears. With a bit of luck, he'll attack David and you can swoop in and knife him. Try to repeat this for the next two runners but if you have no choice or it takes too long, brick+stab one of them and lure the other one into David's arms, then finish him.
- Two clickers will be approaching now. You can kill one of them with the rifle, then hide behind the container in the center and hope that the second clicker grabs David. Knife it.
- Ellie will now shout that the infected are on the roof. Once you've cleared the two clickers, you should run upstairs and aim with your bow at the window where the infected will come from. Once the first dude is in sight, shoot him with an arrow and pick up the arrow again. Repeat for the next infected that comes right after him through the same window.
- Next part is kinda random so you need some luck here. Be sure to stay on the run ALWAYS and keep a bottle and brick on you. Always have the brick/bottle equipped and ready to throw. Keep your eye on David and rush in for a kill once you see a chance. Best if he's surrounded by two: brick+stab one, then finish off the other when David staggered him. Repeat for the rest of the infected. Don't take any chances with clickers: kill them with the rifle if they pose a threat and if David isn't around to stagger them.
- Once David comments that you're doing prettywell, retreat to the long hall and wait for the first runner to come out at the end of it. Kill him with an arrow and hopefully you get it back. What I do next is throw a nail bomb at the opposite end (where it connects to the big room) so I can't get overwhelmed. Once it goes off, there should only be around two remaining runners/clickers that come towards you. Finish them off.
- Bloater should be next. Run up the stairs in the big room and throw all the remaining molotovs and bombs you have on his ass. I used two molotovs and only had to shoot him once with the rifle to take him down. Look out for the couple of runners that also spawn alongside him, finish them with any means neccessary!
Tip: enable photo mode and use it to check your surroundings from time to time. More than once I died because I was running around and a clicker or runner happened to be standing around the corner I was running past. Activating photo mode gives you some time to breath, check whatever David's up to and how many infected are still running around. While you're playing, there really is no time to move the camera around so this helped enormously for me.