Having been through Jakarta Halim just after the BA incident in '82 I can also remember a Singapore Airbus which had hit the cloud - the front fuselage looked like someone had worked it over with steel wire - all the paint gone and some severe surface damage. It was there for several weeks IIRC
One other problem that I have not seen mentioned is the damage to the cabin windows. In the early 80's replacement of cabin windows increased rapidly. An investigation revealed that volcanic was caustic and if the windows were not cleaned thoroughly after an encounter with the ash, crazing and delaminating could occurred.