To judge where to paint the markings on the texture map, the schema could be applied as a texture using Blender. Due to the schema's directional nature, a simple projection might be sufficient. Will try with the profile view.
Update: I didn't end up doing this, but found it helpful to paint a rough guide to the dragon's markings using Blender's texture painting tool. I could then export the unwrapped UV with rough markings to be properly painted in a painting app.