I'm a fucking idiot and wrote a whole big thing and then exited the screen before posting. Because I'm smart like that.
But first off, thank you!

For sharpening, I always sharpen on a new layer using unsharp mask.
I usually use these settings (http://i.imgur.com/9LowntI.png), I might play with the radius depending on how blurry the image is, but I also might just create a new stamp layer and sharpen that one again.
For oversharp parts I tend to use a mask and erase with a mid to low opacity brush, if its still too sharp you can always go in on the layer (or generally a new stamp. I'm all about new layers in case I fuck something up.) with a blur brush.

And then for hair, I might also use a soft light layer and draw in some shadows and highlights.

Lemme know if you have any questions or want any examples? I rarely save PSDs but I can usually whip something up.

Awesome tips! Thank you! <3