Re: Skin retouching- upper lip hairs/peach fuzz
Did you add a lot of contrast to that before posting? Typically peach fuzz is nowhere near this obvious. It also looks a bit heavily sharpened, which makes the rough edge on the lip makeup more obvious.
Her skin is not bad. It is normal. I would start with the pieces that bother me the most and a small clone brush, probably 2-3px 20-40% hardness round as a starting point. I would carefully choose neighboring areas to clone from and just clone out the biggest pieces of each fuzz. I would preview my work on and off to make sure it doesn't interrupt the pattern or flow in any way. If it's just slightly uneven at the end, the burn and dodge tools can be used for minor adjustments.
After you clone out the most noticeable items, you'll see that your eye no longer gets stuck on the others. They no longer matter and it will look better if you ignore them rather than try to polish out every last pixel.
As for frequency separation, I don't see why that would help. Perhaps you can explain what you hoped to gain from it? If you're relying on something that just happens to make most minor problems go away with little effort, then you are effectively dooming your own work. I have probably done that at times myself, which is why I wouldn't suggest it to anyone else.