After watching a few youtube videos showing how Chuck Close gets around in his wheelchair along with a detailed explanation of his work, the students grid their own images. For some classes, I actually take a digital picture of them, put it in GIMP (a free editing program), turn it black and white, increase the value ranges, brighten it, and then posterize it into 6 different values. The students then grid them off and also grid a larger sheet of paper. They transfer their drawing onto the larger page. I have had students sketch them and paint them in the past. For some classes, I have them use magazine images.