You should use the markers instead of the coloured pencils. Then the hand has to be more "free" and continuous. Also for a drawing to look nice has to look dynamic. One of the professional markers are the Copic made in Japan. Also you can try one of the tutorials found on this link:

http://www.style4cars.com/index.php?option=com_content&task=blogcategory&id=80&Itemid=81

Anyway nice try! Keep up!