Sky rail is the shortest action stage in the game, but that doesn't make it much easier to optimize. having the air shoes upgrade (light dash) in this stage is not helpful, and can actually mess you up or even kill you in this stage. It is recommended to skip that upgrade entirely in a dark story run.
Story mode strategies
There isn't much difference between the recommended story mode route and the IL route for this stage, but there are several very dangerous and precise tricks that aren't recommended in a story mode run, so learn the basic story mode route first and add in IL strats only when you feel confident enough with them.
The Beginning to Checkpoint 1
At the beginning of Sky rail, immediately hold B or X to crouch on the rail. When you're at the bottom of the rail, simply go off of the end without jumping. Pressing A here will either make you rail switch and most likely die, or do a trick which is wastes time. when you go off of the rail, hold forward and aim to land on the metal "arm" connected to the edge of the ground. once on the metal platform, homing attack the spring on the end of it to take you to the next part of the stage. Taking the spring at the end of the metal arm is faster than taking the spring pad to the right.
As soon as you land after hitting the first spring, run forward and turn to the left, there will be a small gap between a fence and a barrel that you should jump through. Your goal here is to land on the edge of the platform with the rocket shortcut with enough speed to run right on top of the platform. If you land on the edge of the rocket platform without enough speed to make it on top, simply perform a somersault to get on top. If you miss entirely, there will be a spring in front of the platform that you can homing attack into.
Now all you need to do is take the rocket to the first checkpoint and your done with this section.
Checkpoint 1 to Checkpoint 3 (skipping checkpoint 2)
When dropping down from the rocket, hit the speedpad below you, this will get you onto the rail. The rail goes down in a straight line, and than curves in an S-shape. When the rail is about to move down to the right, do a jump off the rail and jump about 90° to the left. There below you, you will see a pumpkin head with a couple of rings on it, drop down and homing attack cancel onto it.
You can see a spring on the head, but don't use it. Instead, do a spindash jump over it off the pumpkin head to jump over to the next pumpkin diagonally to the left. From there you do another spindash jump to another pumpkin diagonally to the right. For the spindash jump off this last pumpkin you want to make sure to not jump from the middle, but slightly off the middle where the head angles downward. This will function as a very small ramp, and give you extra height for your spindash jump, so that you can make it onto the large roof at the top of the mountain. From there you jump over the fence and you reached the next checkpoint. If you are getting stuck on the roof, try using a somersault jump.
Checkpoint 3 to The Goal Ring
*explain both the homing attack cancel method and rail switch method to get enough speed for a trick on the second rail, with video examples of both strats
*explain backup in case trick at the end is missed*
*explain details about completing the stage*
*video example of recommended route here*