If you are drawing on paper, it would be best to use a regular pencil. If you are using sketching paper, use a good quality sketching pencil for a 6b. But, when you are lightly sketching out the portrait, use a 2hb pencil to do all the sketching, and use the 6b for shading. Start with a round shape for the face and or head. Add the facial guidelines, and then draw position bar line that dictates the pose of your face that you are drawing.