Applying tonal values simply

Every time I teach a class, I usually learn something new things or gain a deep understanding (and appreciation) for whatever I'm teaching. It seems to be true for most things. What I teach others, I learn it better myself. 

I'm presently teaching a pen and ink class and we've come to applying tonal values simply. And here are some sketches I've done on my own time. I've kept it simple by putting ink in my water brushes. But I've been experimenting with using different tools for the lines. Here I've dipped a twig in indian ink.

 

And below, I've used a Tachikawa tank nib. Oh but I tried something different. I first did a rubbishy mark on my paper first. Then drew Roger over it. I felt that made me more carefree about filling the page (because it was already "ruined".) But actually, it made the page more interesting.

Here is a video I did on putting ink in my water brushes. You can also follow along with the tonal value exercises in the video.