Move towards the front of the train. Take cover any place you can find. Kill Locust and move forward.
Keep moving forward. Watch the fuel tank. Try not to blow it up. You may need it later.
When you get to the door, push the button. Marcus will tell Jack to open the door. Then Marcus will hear a dreaded sound. Sweet. Another berserker.
Head back to the fuel tank. Throw a hand grenade at the tank. If it works the car with the berserker and fuel tank will fall off.
Get back to the car that had the door Jack was opening. Go through the now open door.
Baird and Cole will saying Hoffman picked them up. Hmmm Lucky them. Go through door to next car. Locust will attack. Including Reavers outside the train.
Move forward killing Locust as you go. At the front of this car door will be on right side. Marcus will be outside. Run from cover to cover killing Locust.
When you go inside the next car, go forward and enter the hallway through door on the right. Climb the ladder to the roof.
Run to a chain gun and use it. Kill the flying Locust. Once you kill them all go back to ladder and climb down.
Once at the bottom of Ladder, go through door. After the conversation with Anya jump the wall in front of you. Run for the next wall and jump it. Wretches will be attacking you.
Go in to the next car. Kill any wretches you find. Keep moving forward. When you exit this car head to right side of next car and push button. This will release the canisters.
While the canisters are dropping go back to the left side of car and hide in their from the Reavers. When the canisters are done dropping, head back outside and to the right side.
Run forward and duck in to the next car.
Walk to the door at front of car and to the right. The door won't open, so Marcus will tell Jack to rip it open. Wretches attack while Jack is opening door.
Once the wretches are dead and the door is open, Head through the door. Just run across the car since you have 40 seconds to reach a car two cars away. On the second car with a button next to a door, you must push the button a few times.
When the door opens head to right side of car and push button to release the canisters. Wait for the canisters to fall. When the canisters are done falling proceed forward to the next car.