Well theres 2 different ways that I learned..
One [the way I did it] Take the razer blade like on the clippers[take it OFF the clippers!], take a small section, and just run it kinda up and down just to the length you want. So it cuts it basically, but gives it that more natural look, rather then a straight edge. Its hard to explain.
Then the second way, is to literally take hairs like from under neath and pull them out with a pulling comb.
The way I did it, you don't actaully pull it out of the root. And it doesnt thin it out.