Good work. I enjoyed reading the narration of your experience with this build.
Simon O'Neill speaks truth, but here is my additional two cents on edge coloring:
Caran d'ache Neocolor II water soluble wax crayons. (
Caran d'''Ache Neocolor II Aquarelle Artists''' Pastels and Sets | BLICK Art Materials ) Especially good for folded edges. Can be used like watercolors by dipping a brush in water and then swabbing color from the side of the crayon in order to get into tight places. The crayons can also be sharpened to a point. It was Alan Wheeler who put me on to these.
Faber-Castell Pitt Artist pens (Art & Graphic) or Tombow ABT brush pens (Dual Brush Pen - Art + Craft). Unlike marker pens, these are not prone to bleeding into the adjacent areas. Excellent for edge coloring, not as good for coloring folded edges.
Expensive, but they last a long time.
Don