These are samples my co-teacher-tutor and I produced using the same media but with a varying application of the technique.  We both treated the white paper with charcoal buffed to achieve a mid-tone value after having taped the white drawing paper to the board.  Mine is more extreme in its range of values. Whereas his is more in the mid value range. Both are totally acceptable results.

 Art often teaches us that there are more than one correct solution to a challenge.

 Students learn that the buffing process is a slow yet vital aspect of this project.

 Process, media and techniques matter.

This is the value range we want.  Now the student-artist can study themselves and begin drawing with charcoal and the eraser.