OK, you don't like the idea of 'clicker training'. So you'll need to think of another way of teaching/reinforcing 'good' manners.
I think it's worth considering WHY you feed it & what healthier alternatives may be better. Just because you've always done it doesn't mean to say it's a good idea. Just because you haven't seen obvious health probs yet(tho I'd say cribbing is pretty obvious) doesn't mean they're not there or won't happen. Many eat junk food all the time without getting diabetes or have smoked for years without cancer... just IMO it's best to avoid unhealthy choices when possible though.