Well, the prevailing theory among many psychologists is that brainwashing is limited in what can be accomplished.
Although this is debated and there are questions about how genuine the result would be.
For example, the brainwashing in Maoist China was able to get people to turn against free market ideas and to even turn on friends/neighbors. It was able to get people to suppress disssent and to support the state, at least outwardly.
I would argue that you aren't going to change a person's virtues or principles. It would be very difficult to get people to, for example, suddenly not care about family values and having healthy children/relationships. You're not going to convince them those concepts are wrong/bad or prevent them from protecting those virtues.
What you could do, however, is try to convince them that their ways were damaging and destructive while the new way is the better way. You would saturate them with as much evidence - real or manufactured - for this and subject them to peer and group pressure. Implant people who pretend to like the old way, then flip and support the new way. Develop the atmosphere that every rational and sensible person can see the new way is better and you are just clinging to useless sentimentality or superstition with no evidence.