We have quite a few MUPs. As the numbers of users have increased there's been a bit of a concerted effort to tell EVERYBODY to keep right / move right. This can be uncomfortable for people walking but it does greatly reduce congestion and conflicts. People are encouraged to walk/ride two or three abreast but to be considerate of others and quickly move right to let others in either direction get by. Dogs are ALWAYS to be kept to the right of the path.
Bells have also been pushed instead of 'on your left' and this has helped. There is some debate about giving a single ding when passing someone. My personal take is if there are few users then we'll ding the few people we pass since they are less likely to be expecting us. When there are quite a few people I don't bother as it's much less necessary unless someone isn't moving right.