The process of brainwashing is indeed a difficult one. I am given to understand that it can be done, but drugs make it easier; without them, the human mind and instinct for self-preservation is well nigh incontrovertible.
From what I recall, most people placed under certain conditions can be forced into repeating or believing anything. Usually control over their diet, their sleep patterns, and activity is required. Witness the willing confessions of Stalin's purge victims. Very weird stuff. It was the rare individual indeed able to withstand that level of manipulation.
That being said, The Watchtower wishes it could brainwash people. What it does is flood them with repeated information and mindless activity. These are aspects of cult activity: but the participation is voluntary. Once the spell is broken, the human mind can recover.
But it is more of an abuser / abusee relationship than a brainwashing relationship.
I think many people use "brainwashing" as a way to describe the flood of false information; rather than using it in its strictest "Manchurian" sense.
CZAR