Back drawing at the NPG

I went back at the Friday night drawing class at the National Portrait Gallery. I have talked about the Lateshift programme before. I’m not Leonardo DV but I’m comfortable with a pencil.
But i forgot there was a brief.
This time it was to take two pieces of paper a pencil and a marker. First on the larger piece of paper to just create the shading, and then to place the second peice of (tracing) paper over the top and complete the detail. It was actually really hard. Its like drawing backwards for most people. I think the most common approach is to draw the detail and structured lines first, and shading is essentially filling in.