This video gives a step by step explanation of how to introduce your students to fractions and/or portrait drawing.
Susan B. Anthony as portrayed by a 3rd grader. The fractions and support lines were left for this to count as both a math assessment and a social studies assessment.
This student created a self portrait for an art grade, and so he was able to erase their under-drawing. Sometimes students draw on pink or brown construction paper, or tag board to give a little skin tone to go under their colored pencil, and they can color the background in with marker. He cut out the figure and glued it to a different colored back ground for a little more figure-ground contrast.
I have had students who were completely blind complete this assignment using Wiki Stix. One student, also did some graphite drawing on his piece.