There are three shortcuts in this track. The first one is just after the first turn, to the right, on the clouds. Having a mushroom is a must if this shortcut is going to be used. The second one is to the right of the ramp with an item box above it. Having a mushroom is not necessary for high-acceleration cars such as the dry bomber. The third one is before the second bridge, to the left, using the cloud to cut across the hairpin.
However, another shortcut is accessed after you've passed the second boost ramp next to the second wooden ramp, only you need a mushroom to access it. The shortcut is behind the two ramps. Use the mushroom and hop over the gap and then make a sharp left to go back on track.
Anyone with high acceleration cars such as Dry Bones or Yoshi to save mushrooms.