I really appreciate all the input!
I don't see a lot of rubbing now but he still has large nare patches where he's rubbed the coat off and I'm not happy that we've sorted it out.
I think shampooing is a great idea. It's been very cold this week but as soon as the temperature goes up I will do that. Possibly tea tree shampoo? I will Deosect them again as the rubbing definitely reduced after that.
I wanted donkeys for such a long time and they really are the sweetest, loveliest animals!