Thank you for that!! I think your work is great! - I would say a good thing to do, is zoom right in to your paintings, so you're working at 100%, then when doing finer details, like eyes, make your brush hard and small, then brush in the details, to sharpen features - thus making it look more realistic... Another thing you should try, is using a brush which is 20% (or less) opacity, with a soft brush, to add different tones to the skin, then use the eye dropper tool, and sample the colour you have just put down, and start using that on the 'edges' of that colour (if that makes sense), to blend it in... I hope this helps!!!