Once you've completed the game go to chapters, chapter 13, practice speed run and I would suggest running it on easy.
This one is pretty straight forward. Just be careful of the signals around the train tracks. I would suggest restarting if they take you out more than once.
This chapter ends when you reach the tunnel for the first time so not as daunting as doing the whole train section.
Remember to use the valve to open the last car, and overall just try and keep moving forward.