Growing up in a small logging town in Oregon, one of my first pairs of shoes was full-grain leather boots. All my Dad’s friends were loggers. They had breaking-in a tough pair of boots down to a science.
The first thing they taught me was to wear my boots around the house with damp socks. Not dripping wet, just a little damp, and to wear them every morning for at least a week or two. The moisture helps soften the leather from the inside out.