App(s) used : ibisPaint X and Pinterest

Original pic :

Tutorial :
1. Fill in the base of the skin

2. Select it

3. With a darker color, make the shading by filling in darker sections.

4. To make the shading more prominent, use an even darker color.

5. Lower the opacity of the shadings.

6. Use white to add highlights, and put it in the middle if you aren't making face vectors.

7. Lower the opacity and add another layer of white in the middle of the face.

Done!

○ n o t e s ●

I THINK after this tutorial, I'll teach full face vector, hopefully.