When I teach a one day workshop I am always guided by the skill level of the students that have signed up for the class, the experience of the group dictates the lesson I teach. Using masking tape as a resist is my beginner lesson; it's a good way to practice layering with washes and to think about composition in terms of basic shapes.
Today we did my favorite, "the tree lesson". I am going to need to decide tomorrow if I want to add some orange tones to the mountain in the background. I didn't want to make my composition complicated but I did want to add more details than just wash layers.