I usually draw using graphite pencils are rarely use charcoal (Graphite pencils give me better gradations that what charcoal does, or probably I have better control over grpahite, either of it :)). I try to find a reference picture that has distinct shades of light, which also includes perfect white light and thin white strands of hair. What I have struggled to find over the years is a good white graphite pencil that blends well with the black, as well as stands out clearly amidst all the darker shades. I tried prismacolor graphite pencil, white charcoal pencil, Uniball 0.7 white gel marker, indenting and negative drawing method , but not of