I was teaching Type 1 a few years ago and noticed that the students were really having a hard time with white space around their letter forms. After a few false starts, I went back to how I learned the concept: from printmaking, specifically letterpress. I had them bring in erasers that we then collectively carved into our own letters.
In one glorious and messy day, the students started to grasp leading and kerning with ease. I was asked to help rewrite the course and was able to incorporate this lesson for all future City Tech advertising design department students.