Gradient shading technique: you can use it in your fashion illustration because it’s a fine gradient (named sometimes “dégradé” or “passage”) from black to white or from one color to another. We insist upon the figure we want to shade and we come again and again with grades of gray because the most important in this technique is not to leave marks of pencil. Everything must be compact,like printed.
See shadings from white to black in gradient technique here:
It is very important how we keep the pencil in our hand (the inclination of the pencil), the hardness of the pencil and the paper quality itself also.
Some paper brands I recommend: Canson, Fabriano, Tiziano
Each paper sheet has two different sides. One is good for drawing (it’s the smoother side), and the other is better at watercolor or charcoal compositions (being a little bit textured, granulated).
We could use grading at 45 degrees, vertical or horizontal like here:
See here how smooth the gradient should be: