Update to my last post: the Timberland Boot Kit helped a bit, with a few cycles of brushing and cleaner and then conditioner. But what ultimately helped most was dried bread. :
Cleaning & Protecting Timberland Boots | Official Guide | Timberland UK
TIMBERLAND | Boot Kit
Boots Cleaning Guide | Let see how Timberland clean our iconic boots.Step by step and guide on how to clean. #TimberlandMyanmar | By Timberland Myanmar | Facebook