Gary Griffaw
Looking at the drawing of the posts from the Lesson 1 (the last one in the lesson), thinking about the shapes can help, but you need to be careful to not simply draw the shapes that you have in your head. You may end up with lines or shading in places that you shouldn't because you drew the shape in your head instead of what you see. The shapes can be a guideline.
I found when I did the mirror writing exercise that I still tried to think of them as letters. Some of the time I drew the letter more the way that I think the letter should be written than how if actually appeared in the original image.