Well, like a hundred thousand times, my suggestion is the same. Change the 4 special vehicle controls in such a way that you get a feel of pressing the 4 arrows.
In simple words, make the following changes to your vehicle controls :
Special control Up = Home
Special control Down = End
Special control Left = Del
Special control Page Down
Now when performing Hydraulic moves during the mission, hit the respective button as soon as the circle is half inside the ring. If you still can't pass it, just upload your savegame file and you will get the mission passed.
Hope that helps
EDIT : Done. http://filehaven.net/5f0w7yz1wkqq/GTASAsf6.rar.htm