That's a good method. I used something similar when I did an animation of a sewing machine making a lock stitch. This is the first frame:
http://farm8.staticflickr.com/7093/7155097606_c0c1cc4f05.jpg
And part of it when you zoom in and use Perspective mode.
http://farm9.staticflickr.com/8160/7155097396_7060a07715.jpg
Everything but the tensioning knob is drawn flat but they are at different distances from the camera so some things are partially hidden behind others.