Advice for painting skin

Subtle colour variation is crucial for illustrating realistic skin, but it can also take a while to blend convincingly. To save time, I’ve reduced this principle to alternating between the cold and warm hues that correspond to value zones: if light is warm, then shaded portions are cold and darkest shadows warm again, and vice versa. The transition line between light and shadow should be slightly more saturated. Skin is slightly translucent, and so bright light will shine through it, especially in areas with prominent bones and/or less muscles, such as the cheeks or fingers.