QUOTE
I spent a lot more time with the original outline drawing of the shoe (which was the simplest part, theoretically) than each part of the shading,
Not sure what Cindy's teaching (except that she's obviously teaching the right stuff, judging by everyone's results), but one thing I see again and again across different sites, and in my own learning process too, is that people tend to underestimate the importance of getting the initial placements and proportions correct, and try to hurry this stage along, thinking they ought to be able to "just do it", quickly, and that the "important" and "advanced" stuff is to do with shading and rendering.
I'd suggest that its important to realise that getting initial placements and proportions
accurate is something that is well worth taking lots of time over, and that its
OK to spend time doing that - we often see work that is very well-rendered, but where the drawing (or painting - I see lots of oil-paintings let down by inaccurate drawing) looks "wobbly" because those initial proportions and placements have been rushed. Take your time,
enjoy the process of getting your proportions/placements/outlines accurate - it can be slow at first, speed comes with experience and practice, but prizes don't get won for the fastest drawing, but for the best one.

Dave