I´ve seen that many books of technical excercises recommend practicing hands separate, slow, REALLY LOUD, with exagerated finger articulation.
I´m southamerican so the original texts are in spanish:
For example:
ORIGINAL:
"... se empezará a estudiar con una mano, luego con la otra..."
"... muy lentamente, con toda la fuerza posible y la completa exactitud de cada nota unida a la máxima articulación del dedo..."
ENGLISH:
"... must begin studying with one hand, then with the other"
"... very slowly, loudest as possible with complete accuracy in every note plus maximum finger articulation..."
Hans Von Bülow (Liszt´s direct disciple), from Cramer Studies.
Other language versions says de same?
Bülow himself recommends using a mute keyboard:
"... el teclado mudo, que el autor recomienda adoptar, será el mejor recurso en tales casos..."