Mary detail from unknown artist

Once again struggling with shading of skin tone. Teacher said I should be working in oil. Apparently acrylic dries too fast to get smooth transitions in tones. I tried to paint fast with prepared variations of skin tone. Also had trouble with the hair. At this point I can do just as well with pastel and that's not good. While the original has rosy cheeks, chin, and nose, most of the rest of the face is more tan than I was able to get. Going back to fix things at this point would likely make it worse, since acrylic dries darker than when wet, so it would be very hard to mix appropriate colors.