Have Ashley hide in one of those brown boxes near the start of the area. If you do not have Ashley hide, she will get in your way. You will need to save up your ammo for the Bella sisters so shoot everyone in the head, kick them in the face, and then knife them when they are on the ground. As for the Bella Sisters, you need to get into a corner where you can see both of them at the same time. Aim for the head, or for the legs. Flash Grenades and Flame grenades work well on them. When you are at that area where the sisters first show up, knock down the ladders so that you can shoot at them while they straighten the ladder back up.
Any more help you need, I will give you.
Great, I'm moving. Who knows when you'll see me again.