They should do one of two things:
(1) Make things as easy as possible. Find all the places where mysticism exists and root it up. That would mean a truly objective study of the original Bible, including all the books that the Catholic church threw away. Realize that the reason for the confusion is partially because Paul mistook Jesus' words literally (if it suddenly makes sense, you have probably stumbled on the real truth, or a good part of it). Alter the core doctrine accordingly, and encourage independent thinking as Jesus did. The religion would then cease to be a destructive cult, children would be willing to stay in, people would investigate it and find the true solutions without being forced to fake anything, and they would help lead the way to the paradise that is really paradise (and not stagnation).
(2) Crack down on everything. Enact the ban on entertainment. Make everyone spend 250 hours a month, or more, of difficult field circus and cross check to make sure every minute is accounted for (so they can't turn in fake time slips). Ban all medical care. Explicitly ban any activities that could generate any fun. Give them longer boasting sessions so children would be up at 2 AM on school nights, and 6 a$$embly weekends (two that would last the whole week) per year. People would then start deciding that they cannot do it, and would simply not show up for field circus or boasting sessions; children would all quit (and most parents would qult letting them stay up until 2 AM on school nights, and would likely walk out when the hounders chew them out about it). You would see a tide of disfellowshippings and disassociations, with only a very few humanoids left in.
Either way, it would spell the end. Either you totally release the mind to live up to its full potential (and end the destructive cult once and for all), or you lose all the followers (you cannot mind-control people that are not there).