You can use whatever you want- Copic-Markers, pastels, water colour, soft pastels. I usually use more than one material. I mix soft pastels, markers, liner pens and Milky Gel pens.

This time I used Artists Colour Pencils Polychromos from Faber Castell , black liner for the contoutrs, white gel pencil for very glossy areas or highlights, a kneaded eraser- great for highlights and softening of too dark areas and a eraser pencil for pin-point erasing.

Polychromos have very soft waterproof wax leads. They are smooth and resistant to smudging and can be used on paper, card, wood, or even fabrics. Pastel pencils in contrast have more softer leads, so you can easier smudge them but they also break easier- they are good for highlights and shadows but I prefer polychromos for drawing something in detail.