Hey I'm in the process of learning it myself but I saw a tutorial where they dipped a paintbrush in a small amount of a darker tone (possibly a more reddish tone than skin tone)and used their finger to rake across the brush, flicking small amounts of paint onto the head. The artist then painted over it with a thin translucent coat of skin tone to solidify the look. I don't know the specific tutorial but if you look on youtube searching "1/6 head painting tutorial" I'm sure you're bound to come across something. I hope this helps.