hey dave welcome to the daggers man
its truely admiralble for a man of your age to still have the desire of self improvement
fuckin-A
few things i want to point out,
you need to push your values, i can see youve grasped local value those two girls both have differnet local values but their not being pushed esspecially in areas were an ambient occlusions occur on the figure were light would have a hard time reaching.
heres a paintover id did of em 45min each
didnt know what kind of ref you used so i winged it from imagination, it showed me i suck at alot of things lool
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you see how i managed to push the values but keep their respective local tones
its easy when you think about values as numbers the first figure has a local value of 2 so the maximum darkness you can push for that object without it looking weird is 6-6.5
the second figure looks like a 7 in value so the darkest it get is a 8.5 or a 9 in the occulsions like the armpits or the little spaces around the boobs
the rest is just drawing
use soft edged brushes for soft things and hard edged brushes for hard things... simple right
but alot of ppl when they start out they do other wise, the result is that muddy digital rendering we all should avoid like the plague, this isnt a soild rule you can use just hard bushes but you have to apply a more traditional midset like if you were working with hard media like charcoal, conté and pastels.
Hatching, blending and manualy changing your hue value an chroma , check out Craig mullins for that approach
be mindfull of your facial/body proportions
going for the stylised approach is no excuse for not studing anatomy, once you understand it you can create more powerful stylised work
remember "Style" is the fundermentals skewed to the voice of the individual
look forward to seeing more man
happy painting :)