Hi Luiz Cesar!
My sugestion:
Give your self a challenger:
Put there 6 plates (paper made pherhaps..)
Draw and Hit one shot each, at a time (for example 6 secs..)
When you reach this, go to 5,5 secs
and so on...
You will be stoped in your own skill limit...
So, try to go beyond it!
Its amazing, develop precision and what you need to do, to be faster and faster, but inside your skill level at that moment. Seems to be easy, but isn´t !
Um forte abraço!
Ramos