well , i don't putt the charcoal pencil on paper for painting the surface , you can use brushes and also use the sand paper to make some powder of the nib of pencil, then use your brushes and paint , or you can use some cotton to blur the edges , oh ,, there are some different materials you can use , watch videos on youtube and you will learn ,its not a big deal :)

white details i use a tiny eraser , and usually i don't paint the white surface , its the whiteness of paper