I’ve determined that the charcoal pencils I use are best for linear drawing but not shading.
Despite the drawback of not being able to shade very well with these pencils they are the best for getting accurate lines down on the page which I think is the most important. I must quantify this though. I really mean that these charcoal pencils (conte a paris) only work well for shading if you are willing to spend a few hours on working up the values. This is much different than vine charcoal or other compressed charcoal where I’ve seen artists work up the shading rather quickly. I’m going to have to being experimenting with other types of charcoal.