Here are some exercises from the Alfred Cortot's book "Rational principles of piano technique."
According to A. Cortot the use of the still finger allows to minimize the participation of the hand to the production of sound and, in addition, favours the individuality of attack of other fingers.
In these exercises you need to keep a few fingers pressed while the others move. Braille symbol appears in the right hand, but the same exercise can also be done with the left hand. For example, in the first exercise, thumb will be the finger that will remain still, while in left hand it will be the little finger.
The sixteenth notes will be played first tied and then detached. According to A. Cortot these exercises are among the most effective ways to develop the independence of the fingers.
Exercise No. 1
Fingers still: right hand 1, left hand 5
Braille example
Exercise No. 2
Fingers still: right hand 2, left hand 4
Braille example
Exercise No. 3
Fingers still: right hand 3, left hand 3
Braille example
Exercise No. 4
Fingers still: right hand 4, left hand 2
Braille example
Exercise No. 5
Fingers still: right hand 5, left hand 1
Braille example