I'm with JAWS on Kylo having control of his actions. In SW, the dark side is the metaphorical representation for making bad choices. If someone (be it Kylo, Vader, or Luke) could be brainwashed to simply act out Palpatine's wishes, there'd be no point to almost everything Yoda said in ESB.
At it's core, SW is about morality and family. The choice to do the right thing (the more difficult path) or the wrong thing (the easier path) is where the individual has the power to influence destiny. Personal accountability is at the heart of it. Brainwashing to the point of making people act against their will would be something completely different.
The value of the redemption arc (like Anakin's) is in the value of having the power to make redeeming choices. The individual is in control. The whole purpose of training to be a Jedi in the OT was to learn how to be calm and passive; to use the binding energy of the Force to resist the temptations of fear, anger, and aggression.
A fully trained Jedi Knight would be able to resist the temptations of the dark side. Such a Jedi would know not to give in to fear or hate, and not use the Force for violence and destruction. Luke graduated to that level of awareness, whereas Anakin hadn't. It's all spelled out in dialogue from ESB.
YODA: "Only a fully trained Jedi Knight with the Force as his ally will conquer Vader and his Emperor. If you end your training now, if you choose the quick and easy path, as Vader did, you will become an agent of evil."
Yoda felt that Luke wasn't ready because he had failed the trial in the cave. Luke acted violently (because of fear and anger). In so doing, he was following the same path as Vader. Yoda and Kenobi weren't preparing Luke to resist brainwashing (which would be impossible), they were preparing Luke to learn *control* so as to resist the consequences of giving in to dangerous emotions. Luke had tapped into the Force, but hadn't learned control to use it wisely.
KENOBI: "But you cannot control it. This is a dangerous time for you, when you will be tempted by the dark side of the Force."
YODA: "Yes, yes. To Obi-Wan you listen. The cave. Remember your failure at the cave!"
All of this is about personal choices and accountability. Something like "brainwashing" would totally move away from the whole point of what Lucas was getting at. No matter if it's Luke, Anakin, or Kylo/Ben . . . the message of each arc is about what kinds of choices are made, and for what purpose. Each of them chose their paths (for better and worse) based on family issues. Luke shows the audience how to choose correctly. The other two are cautionary tales about how choosing poorly based on negative emotions will only corrupt your soul. Introducing brainwashing into any of this would negate the thematic takeaway, IMO.
The st changed all the rule so citing anything that occurred in the ot is irrelevant espcially what it comes to what the force can or cannot do. What i will say the mind brainwashing was established in the scene khev linked in the pt the only reason he didnt use it on anakin was because as i said earlier it would have alerted the jedi. He only did after his after his cover was blown. With kylo its full on brainwashing in his head the whole time they even say it in the movie