This safe house is one of the ones you want to move out of quickly – special infected may lurk on the roof. The farmhouse a little ways down the path may look like a great place to search for goodies (and it is) – but it can be a death trap in versus mode and can be nightmarishly hard to defend. Look around, grab what you need, and move on.
A little further and you will find a building and the train tracks. Ideally you want to leap from the embankment across to the roof – this is a good vantage point and helps you avoid a possibly unpleasant ambush. Take out some of the infected down below before hopping down to the tracks. Watch your fire here, as there is a car that can be set off. Move quickly down the tracks, stopping briefly at the first house to look for supplies.
Enter the side door on the next house and check it as well. You will likely encounter a tank here – evade it outside the house to minimize damage. Also, near the door where you entered, you can jump over the railing, behind the fence, and circumvent the house entirely. The tank will be hard pressed to follow. This is undoubtedly a cheap and unintended tactic, but it can help you avoid the tank completely. From here it is a straight shot to the train car where the safe room is.
Once again, hit the ground running after leaving the safe house. You want to be far away as soon as possible. Keep your eyes upwards and watch out for hunters and smokers on the sides of the embankment and on the tops of the train cars. Follow the tracks to where you can climb on to a train car and over a small hill. You will find yourself facing a large open field. Make sure your team drops down all at once or special infected will be able to pick stragglers off.
This part is unpleasant for everyone involved, so as long as you are not being swarmed, you need to be moving. Find the tractor, get your bearings, then head toward the farmhouse. There are several buildings nearby, so take the time to check them for whatever you might need before you start the finale, but stay together. This is one of the harder finales, so do whatever you need to do to get prepared.
In terms of defensible positions, the farmhouse leaves much to be desired because many of the walls can be broken through, but downstairs in the room with the radio is a decent place to stand your ground. When the tanks come, head outside and fight a running battle. Stay on your toes, watch for the tanks and stay away from the windows and you just might make it till the army arrives. When they do, jump in the back of the truck and you're done. Congratulations! You survived. For now...