"Brainwash" is one of those words that instantly shuts people down.
If I tell a JW about brainwashing, they just know that they are able to think some for themselves and the idea is crazy to them.
Even here among people who are no longer in the religion, you will get arguments about the term.
Watchtower is a dangerous mind-control cult. But that's just as bad to say.
Given the chance, I would start with "high control" group. And then I would use Steve Hassan's BITE method without identifying where it comes from.