Ricks drawing

Hi Matt- 

This one is a work in progress. I may have bitten off too much trying to do this sheer fabric. 
Im still finding shapes and adding values. But a question I have is how do you handle getting a range of values using white charcoal? I feel like I can get about 6 shades of value with the colerase but only 3-4 values out of the white. So to balance it I tend to not go as dark as I should? I’m using gray toned paper. 
thanks as always! 
(Oh and I purposefully changed the head from the reference, but does it look realistic still?)