These sketches are created on a Surface Pro with a Surface pen, using the Leonardo App. The Leonardo App has several pencil and brush textures, allowing you to work almost like with a traditional pencil and eraser. It gives the impression of the use of pencil and pastels.
These sketches are made with an ordinary pencil. Occasionally I use pastel pencils for highlights and charcoal for the darkest tones. For fine details, I use a mechanical pencil.