What I immediately notice from your portrait attempt is how your features do not align correctly in perspective. I would recommend you to continue drawing Loomis Heads and keep in mind the 3D forms of the face. Pay close attention to how the contours and measurements are parallel in relation to space and form. Use the 3D model as a reference. Before jumping into shading and details, the construction and foundations that make up the face are the most important to get right first. If the measurements and perspective are wrong, everything else after will also look incorrect. As for shading and getting smooth transitions in gradations I would recommend Smooth Newsprint and Charcoal, however, what matters at the end of the day is how you use the materials given to you and making the most out of what you have. Your shading is quite good! Don't give up and continue to reduce the number of mistakes you make each time. Take the time to measure everything diligently, once you think it matches, you can start to jump into finer details and shading. Good luck.