There is a new easiest level to do this on! If you have the ODST campaign, load up Uplift Reserve, make sure the following skulls are turned on and that it's on Legendary, and just blaze your way through.
Black Eye
Blind
Catch
Cowbell
Famine
Grunt Birthday Party
Iron
IWHBYD
Mythic
Thunderstorm
Tilt
Tough Luck
You may want to practice run in through on a lower difficulty first just to get the hang of it, but the level only takes about 3 minutes. Check this video for a good path to take. It took me only maybe 10 tries to get it perfect on easy, but when I went to record this video, it was my first take.
3 spots to point out: You MUST hold
while going over the rail, as viewed in the video, while going up onto the rock immediately after (honestly its miraculous I didn't die there), and one last time at the final little ledge right before the end of the mission.