I was introduced to this useful tool by another consultant a few years ago, and have used the process myself a few times. It works well, but you need time and to make sure that enough of the right people are in the room i.e. those who can make decisions, allocate resources etc. or it won’t work.
It’s best to cover a wall with paper (as large as you can) and let people loose with the marker pens!
There are a number of useful resources for you here:
Article about the origins of the model and how to use it
A session plan I used to take people through the process – very detailed
A summary handout (that may be useful to help participants stay on track)
A handout that can be used for personal planning.
All are unbranded and in word. Please limit them to personal use.