Shading edges

I have been watching a tutorial that teaches shading techniques, here is my work in progress. Initial sketch of the skull sitting on top of a table, I flipped the image and continued to make adjustments to the sketch. I think flipping it definitely improved the accuracy, I should have posted an image before and after flipping it to show the difference! Anyway I guess our eyes definitely get used to starring at one image so flipping the sketch definitely wakes you up and lets you see some mistakes.

Next time will add in the light and shadow. If you are interested in the course you can find it here: https://gumroad.com/chrislegaspi