That’s a lovely rendering Samurai, hand you seen Armin Mersmanns work? For me he blends photorealism into a more drawn style, he is my favourite graphite artist. You on the right line with hair, but it looks as though the erasers your using are either too thick or your paper is too toothy for the style you draw in. I will do a hair tutorial and post it up here next week. The best erasers I’ve found for hair are ‘maped tip top’ you have to buy them in packs of 5 off amazon as not many shops stock them, the edges are really fine ideal for showing strands. I can’t tell from the images what paper your using but something really smooth like Bristol board would compliment your style, your good at getting skin tones to blend and smooth paper would highlight that.
Nice painting PDF, looks good next to your guitars.