the techniques of brainwashing are simple: Isolate the victim, expose them to inconsistent messages, mix with sleep deprivation, add some form of abuse, get the person to doubt what they know and feel, keep them on their toes, wear them down, and stir well.
then put them in a position of vulnerability. watch their every move. give them a reason to be looking behind themselves at every given moment.
and right as they are about to break make it seem like they are fine. keep this up for a while but don't let them think they are okay. at that point of hope, break them again and again until there is nothing left.
you are left with a broken human, void of emotions.
now, do as you please.