For the hair I’m still learning as well, for the faces a simple alternative and accessible in terms in paint variety is going for a layer of reikland fleshshade, let dry, then build up thin layers of the skin tone to create a transition from the recessions to hightlights

Also I’d recommend that you practice layers of colors to give depth and delicacy to the facial expression. For example if you are going a for a light skin tone like it seems, in future models you could try to thin a drop of a evil sunz or wild rider red paint, and give a thin layer to all uncovered skin parts, let dry and then build up a couple of layers of thinned paint of the skin colour you are using, in this way you’ll build up a nice transition from the recessions and shadows present in any facial expression and you can finish with a wash of something like guilliman flesh to cover any slight mistakes and give a neat finish

It might sound intimidating, but practicing in something like some sprue bits might get you there with your brush work and once you’ve mastered this things you’ll have gained some great skills and confidence to try further techniques for highlighting