I recently came across this sketch challenge: draw 100 faces, each in 30 seconds or less. Though I haven’t reached that number of faces at one time, I have scribbled a few here and there — quickly as possible and with ink instead of pencil.
Try it yourself :-). Some sketches prompted by Holly Herick’s 100 faces challenge :
Calligraphy Pen Sketching
MichealCain
Poe
Sunday School Note-taking
sydnikruger.com 
So glad my blog inspired you; that is what I was hoping for. The idea for 100 faces comes from a book by http://www.carlasonheim.com/. She is a fun inspirational artist. I never got to 100 faces either, but I really did have fun creating the 48 or so sketches. Some of them were horrible, but that is the point of the exercise—to just draw without hindrance.