Hee, for me the two characters essentially work in the opposite way to you. I have a crystal clear picture of Draco for each project, but Harry is just a sort of Every Man blob. I think this is because I have never identified with the 'every-man' character. I still don't quite understand how you separate working on the two characters. I don't work equally emotionally between the characters, but i try and balance the attention and process of line drawing followed by colouring,otherwise I will never manage the two of them together coherently. i have more pictures of just Draco though.

In terms of Draco's hair i like either a long style in which he echos his father, for good or ill, or a cropped style in which he consciously rejects his father. I don't think it is possible to be Lucius Malfoy's son and not seek to mark your allegiance to him or not. Either way, he wears it very differently to his father.
Short haired rebel draco (http://fc07.deviantart.com/fs41/f/2009/008/f/6/Thaw_2_by_raitala.jpg)
long-haired draco (http://fc06.deviantart.com/fs43/f/2009/158/d/3/Veela_Draco_by_raitala.jpg/)