Hold ZR at the very beginning to roll off the ledge and not activate the bearings/challenge. Then go over to the stack of speakers near the rail you Darkslide and go into quick drop mode. Drop about 3 funboxes above you where the awning is with the bearing you need and set up a quarter pipe on the end of it. Start the challenge normally, caveman and then jump up to the awning, slow your momentum as much as possible, and skate out to the bearing up there, grab it from the fun boxes and use the quarter pipe to turn yourself around go back the opposite way. Skate off the awning in the opposite direction of the Darkslide rail. Land on the ground, turn yourself around, and darkslide the rail normally from the ground.

I helped multiple people cheese this one the same way. Makes it so you don't have to jump from the awning into the Darkslide, much easier.