hand drawing exercise

this is the first time i've actually read and used the famous book Drawing on the Right Side of the Brain, and the exercises are really interesting. I'd never tried "toning" the paper before doing a drawing, but it makes your highlights stand out like crazy! I think I went a little overboard; hopefully i can do better than this in the future. Below it is a plastic picture plane that I made. In order to do this exercise you need to use that.