Progress Post Project #4

My Project #4 has had a delayed start but I am happy that I've made progress! So far after transitioning from my original plan for another graphite drawing, I decided to do this project with Vine Charcoal and subtraction technique similar to my pen drawing. I was able to start with a solid black background which I blended together. However I'm having difficulties with subtracting the charcoal and erasing it. It is taking a significant amount of effort and time just to erase a small portion which is very different from my pen drawing. There also isn't much difference between the values which I am trying really hard to fix.