I spent around 40 hours drawing this picture, and I've spent dozens of hours practicing hair...for short hair like this, i just paid attention to direction, length, and thickness. start by laying down a 2H layer of the hair in the direction its supposed to go, then gradually build with H, B, etc. until you get it as dark as you want. make sure you layer them so you can properly render it and it doesnt look flat with empty space behind it, but instead looks like a body. Just remember that not all hairs follow EXACTLY the same direction, and some vary by a degree or two. With softer hair, try not to define each hair as much, and make them seem to blend into each other more. Make sure you pay attention to negative space and highlights. I hope this helped!
40 hours??? i couldn't draw the same draw for so long, i would hate it XD i have just end a portait, and i'm not very satisfaced with hair, what do you think? i hope you take a look and tell me what's not good [link]