I don't think you can really wake someone up until they are ready. You can plant seeds, little nuggets of information that will be useful and may help when they are, but you can't force them to see the truth.
It's why buying advertising or billboards or sending letters and all these things to get a message in front of someone are mostly pointless. It's not that they don't know about the messages saying the WTS is wrong, or haven't come across them that's the issue. It's that they are just not ready to let go.
We have to be careful that most of the marketing isn't really only appealing to those who have already left and maybe looking for repeated validation or reaffirmation for their choice.