My parish really has it down. Many people still use the cards, though. My recommendation is to have the choir make the responses loudly with the congregation. It helps it to sound better, and eventually, after a few weeks, it will start clicking with people. One of the major reasons why it goes into a lame mumble is because everyone else is doing it. There’s no one else in the background keeping it going, and when two or three people in the congregation mess up, it radiates from that epicenter like a virus and two responses later, everyone sounds like a collection of dying cats. Therefore, to keep everyone in line and to provide continuity, I really, really recommend having your choir make the responses loudly as well. Then, perhaps after another six months or so, they can start to wean off. In the same way, play to the musical ear. Sing the responses. It goes so far with forcing people to get it right. We’ve done both at my parish and probably 95% of the congregation has it down pat.