dry erase of course
I really can not see anything wrong with your portrait. The proportions look fine. I don't know if you intend to draw figures in the future; but, this work shows you can do it. It would require practice. This is true of anything you want to do. You can do whatever you put your mind and effort to. Get busy and get busy.
Hi Mike! I think your draw is amazing! But since you are asking for critic:
1. Try to pay attention that the eyebrow line should be bigger than the eye width;
2. Are you sure the eye shape should be that flat?
3. I love the deepness that you brought with the shadow in the mouth. What about if you try to bring these on the other shady areas?!
4. You can exaggerate and define better the shape of jaw and cheeks making the shadow in that area following its draw, so avoid something so straight too.
5. Simple and gold tip is to make nervous lines on the neck;
6. I am sure these eyes gonna be gorgeous with some glaring (erase little balls above the pupil).