a) Play every black key once, in any order.
b) Play every black key as many times as you wish, in any order.
c) Place each finger on a different black key.
Move the fingers randomly to a set tempo.
Slowly speed up.
Slowly slow down.
Keep playing while letting the fingers and the tempo go mushy.
Transition to playing the black keys with the whole hand using a rolling motion.
Never feel obliged to follow the directives.
Be curious instead of critical.
There is no right or wrong, only experience and sensation.