Use a small, gentle brush and black paint, and insert delicate shading amongst the middle shaft and both sides with the feather. Keep on with a good, sharp brush and trace the hairline strokes to improve the shading and volume of the feather vanes. Beautiful watercolour from Leni Kae. https://quill-pen-art-tutorial43208.thelateblog.com/34694346/the-definitive-guide-to-quill-pen-art-tutorial