I went to a one-day overview training. Then, I read a couple of books on it (Including "Motivational Interviewing").

Then, me and my field supervisor both went to a two-day intensive training workshop that drilled down on each of those 4 techiques you listed above and included lots of "role-playing" type of experiential stuff.

The reason I think it works so well is because the motivation for change all comes from the client. It all becomes "the client's idea." The therapist helps the client see that they CAN make the changes that they want to make.

So, it's that sort of thing.