Lost count.......... it was more than 20 in 5 minutes anyway......
Its easier if you are using a laptop...... and use both hands one on the mouse pad and the other for the mouse buttons......move the ball so its dead centre of the screen and the string is straight.......
using the index finger that you use to control the mouse pad push up slightly then quickly pull back, this will make the string ball go up and then recoil back....... if you did it straight then the ball won't deviate and as it comes down it will pass over your cursor......... now just time the click using your other index finger........