We got featured on ArtByCe's Youtube channel! I love this video not just because Ce says some very complimentary things about the site ;), but because she shows her whole sketching process. This is different than the technique I personally use and recommend for 30 second drawings, but is just as valid. I hope watching her work gives you ideas for your own practice sessions.
You'll note that she very boldly works in pen, meaning no erasing possible!