I'm going to sort of explain a way that you can cut a man's hair into a duck-tail. Chris' hair is a little on the short side, but basically, just so that you know, take diagonal sections behind the ear and work everything into a V shape, coming towards the nape. It would literally be pointing your fingers in -- I can't really do it because Chris' hair is pretty short -- but the idea being that you're working everything into a V shape through the back.
And again, just parallel sections. Over-direct each section to the first. Continue in a V shape toward the center of the nape. Again, if his hair was longer, what I would do is, I would continue that line down so that you actually would get a really, really nice, tight hairline area with a sort of longer, sort of scruffier back. That will give you a shorter, tighter side area coming down into a nice sort of duck-tail back.