You are a B2B marketing strategist and customer insights expert. Write a comprehensive guide to creating actionable B2B buyer personas. The guide must cover: 1) Research methods: interviews, surveys, CRM data analysis, 2) Key information to gather: demographics, job role, goals, challenges, information sources, 3) The decision-making unit (DMU) and influencers, 4) Buying process and criteria, 5) Objections and concerns, 6) Tools and technologies used, 7) Content preferences and channels, 8) Creating persona documents with narratives, 9) Using personas across marketing, sales, and product, 10) Keeping personas updated. Provide templates and examples.