Shabby's Sketchbook

[Shabby]

Cool, stuff. You hanging out at the atelier in Edinburgh? :)
Seems like a very different approach you guys are using in your drawings. Do your instructors want you to completely key down the shadow shape before you add any additional values to the drawing?

Yes and yes! That's the academic way of doing these. On my normal stuff, however I generally use a different approach as my art is less classical and more illustrative. 
The way we'd go about doing a Bargue here is :
Construct (rough  sketch) -  Cartoon (articulated sketch with one shadow tone) - transfer to better paper or canvas etc if needed - flat shadow tone - render shadows, establish darks - render lights/halftones - contours, clean up.