What you have done here is remarkable. I’ve watched it over and over. It cannot be overstated just how absolute the line is when made with a dip pen. Its almost like you are drawing the portrait with the white of the paper and using the ink to cover up the bits you don’t want showing. Its so so hard to do. I’ve tried to dumb it down by drawing the contour lines as you describe but it’s not as simple as it looks. The spacing between the lines can make the whole thing look a mess or make it dark and clumpy. Also each time you dip the pen you can’t be certain that the first stroke will be thin. It seems to me that there is a world of info regarding how to choose what to leave out! A problem you don’t face in the same way with graphite because you can always lift lines or value later. I wish you could make a small addendum explaining HOW you chose to leave out lines. You do mention transitions from light to dark and breaking the line. I’m missing something. Eish, well done.