Tilda is from the "so special collection " and i've coloured her with darker skin tones ... some people find darker skin tricky ... i use these colours in this order..and this is my favourite copic combination.
It maybe be different from other peoples - but this is how i colour ..
R43 - cheeks ,E21,  E53 ,E33 , E34, E15
I use a combination of small circular strokes and light sketchy brush strokes.
Copic Skin Tone Tutorial .
1. colour cheeks - i use R43 - but any bright reddish pink will be fine
2. colour the whole face with E21.
3.  Using E53 colour around the edge and into the face but not quite all  the way into the middle -
4.  Next using E33 colour around the edge but not quite in as far as the E43.
5.  Now do the same with E34, again not as far in as the previous colour .
6. Go around the edge of the face  with E15.
7. Now blend all the colours gently with E53 going right over the whole face.You may need to practice how much blending to do as it is easy to do too much and have a mottled effect.
You may wish to touch up the cheeks alittle with a slightly paler pinky red.

hope this tutorial was helpful to you x