Yo good progress!!
As I am currently learning this I am more and more realizing that good shading can be tough, you have to be actively thinking about planes, light direction and the types of values and what they do (light and shadow average, midtones - slightly darker light areas, atmospheric light - slightly brighter diffuse areas in shadows, ambient occlusion zones - darkest black areas where no light comes) and then you need to think of design, the abstract shapes those areas make speak a visual language that can help or hinder the aesthetics of your composition. its a lot to take in! I like the smooth gradation and the sparing use of black and highlights
As for brush settings, using pressure for opacity and size isn't necessarily a bad thing. I rarely use pressure size, but use a lot of pressure opacity - just a matter of preference and how you use the brush. Opacity size can be useful for tapering tips like hairs for example
there's always going to be more to improve, keep at it! In this case as for the shading notice the shape of the shadow on the right side of the figure's face and neck, how it's almost this one big abstract shape that goes from the hair line down to the base of the submandibular region and larynx in front of the sternocleidomastoid, then you have a few other prominent very dark areas: the ear area covered in hair, behind the right nasal ala, the nostrils and the eyes. I would keep pulling down the hair a bit more and push the angle of the forehead at the figure's left side a bit more back, and insinuate more volume on her right cheek (the shading makes it look a little flat right now)
cheers! keep it up
