For my Jacket illustration I decided the best way to communicate the wool texture would be through brushos (also watercolours are waay too hard)
Brushos are like powder paints, but more like an ink than a paint. It creates a dye when dissolved in water, and when sprinkled onto wet paper bleeds colour out. After a year or so I have seen the purple fade a bit, but while it lasts it looks fantastic. The results vary alot, sometimes the colours are too dull, this tends to be linked to the amount of water applied, so you have to use quite thick paper to avoid rippling.
Heres my first attempt illustration before putting it onto a mood board.