How do I blend charcoal enough to make it look like a skin surface?
You will probably need medium and soft charcoal for creating smoothly blended surfaces (like her skin), and some hard charcoals or perhaps even a carbon pencil (which contains a mixture of charcoal and graphite) for the crisp textures of her armor and the fine lines of her hair.
For blending, you may want to use a tortillion or a blending stump and a kneaded eraser.

Source: https://rapidfireart.com/ &lt;-- also has many great tutorials on how to shade
Tortillons and blending stumps are tightly rolled pieces of paper with a tapered tip. You can either buy them from an art store or make one yourself. They can be used with both pencil and charcoal, and they're better for blending than using your fingers, since your skin contains moisture and oils, which can cause the charcoal to clump to smear unevenly.
Here is a thorough response describing how you can use a blending stump or tortillon for blending: How do I get a blur effect in pencil drawings?

Source: https://thevirtualinstructor.com/blog/10-essential-drawing-materials-and-tools-for-beginners
A kneaded eraser is a soft, stretchy, gummy material that can be used for lifting, removing, and blending charcoal or pencil. Aside from removing &quot;mistakes,&quot; erasers are also great for blending. This video does a nice job of demonstrating some different techniques for using kneaded erasers with charcoal:
https://www.youtube.com/watch?v=PIAKBVfl_YU

Source: https://phoenixartsupplies.com/art-supplies/strathmore-500-series-charcoal-sheets/
As for paper - there are many different types of paper out there for use with charcoal. You can usually find charcoal paper pads at art stores. You could draw on white paper, like the original pencil drawing. But if you have white charcoals (for drawing highlights), you could use toned paper. This can help make your subject &quot;pop&quot; off the page. For sketching and practicing, newsprint paper is a great (cheaper) alternative.
Here are some good resources for learning about types of charcoal paper and their characteristics:

https://nitramcharcoal.com/selecting-perfect-paper-charcoal-drawing/
https://www.artistsnetwork.com/art-mediums/drawing/best-paper-for-charcoal-drawing/

Hopefully this helps! Feel free to ask any questions. I'm not a professional artist, but I've had some experience with charcoals and pastels. If anyone else has additional tips, feel free to comment below.