Hi Chekdot, awesome page of studies! I'm not sure if you still needed help on this, but I have a few ideas you might find useful for your digital sketching. You say that you feel your lines are too 'chaotic'. In my opinion this is not at all a bad thing, as long as you are creating good shapes. Once you have really figured out your shapes, proportion, etc., you can justify worrying more about nice lines. And fortunately for us, digital gives access to a myriad of tools to reach our end goal of 'nice lines'. I attached an image of one method that you might find accessible and useful. The idea is that you start out as rough as you want, soften your sketch with the Smudge tool(using a soft airbrush is probably ideal) and then on a new layer you can do a more refined drawing with nice line weight, edges, overlaps, etc. And of course, repeat this as many times as you need to! Drawing is quite difficult, and it is especially difficult when we try to get the perfect shapes, nice line weight, and develop our understanding of form all in one mark of the pencil. I think that skill comes only after making thousands of messy or imperfect drawings that are necessary to help us to understand really understand form. It's a strong opinion I have that great shapes will make up for 'messy' lines, but nice lines will never make up for wanting shapes! Hope you find this useful in some way and are keeping up the great work.