Okay, this is going to take some explaining. To use hydraulics, you use the number pad. (On the far right).
8 = up 2 = down 4 = left 6 = right
To get it right, you have to hit the key as it hits the middle.
In later parts of the song, you have to deal with diagonals. What you gotta do is you combine the numbers (eg. 8 and 4 is up-left). I skipped those but you don't have to.
Now if the number pad is not your thing or you have a laptop, go to:
Settings > Controls > Vehicle controls And scroll down to the bottom. Bind the SPECIAL controls to the arrow keys.
Now you should little (if any) trouble with this mission which i found difficult myself.