I usually draw both of them at the same time... kinda. I start with the lineart, then do the basic colours on both characters. Then I do all the skin-shading on one character, then the other. Then I do the hair, and then details xD

And don't worry about it; I'm constantly wondering how to go about it, so... my method is just... how I do it. Obviously.

Draco's hair... usually like Boyd Holbrook in this picture (http://1.bp.blogspot.com/_70rJ1ndenM0/SDhRsAMexrI/AAAAAAAACq4/mpvNVCMB3lE/s400/2008040714502864.jpg) (I hope you can see it :)) Just kind of... loosely combed back XD