Students in my drawing class had previously used the grid method in order to draw out an image, erase the grid, then add value to create a realistic drawing. The lesson we did after that one was a Pop Art Andy Warhol inspired project where students outlined each and every change in value and re-drew it 4 times. THIS project combined both! We gridded out the image they chose (preferably a person or movie figure) and then outlined each value change. They then re-drew their grid on a new piece of paper and then transferred the blobs of value from the original image onto their fresh gridded paper (instead of drawing each realistic line). See some of the works below if this sounds confusing!
Once students had their image re-drawn, they used sharpies to go over their pencil marks, and finally added contour lines to create some value.