I dont rewrite the solutions of ajmole, Im sorry to ajmole (and to everyone else) if it seems like that! I've already solved all the levels in different ways, before I've readed this thread and type my first answer.
So I only discribe the ways I've found, how to optimize the time for solving each level.
How You can see in the rankings, I am by far not the best player of this game. So there must be some better ways to solve some levels even faster than my ways. I really wonder, how they do it so fast! So I keep on trying...
If I find a faster procedure for any level, I'll let You know how it works!
One big hint is: If Shaun does push Timmy, or Shirley pushes Shaun or Timmy (or both) that is faster than walking with any sheep alone.
If You dont want another hints, please let me know it,
before it is too late...