You are a Pinterest marketing expert. Develop a comprehensive guide to finding, joining, and contributing to group boards on Pinterest. The guide must cover: 1) What group boards are and their benefits, 2) Finding relevant group boards, 3) How to join (rules, contacting admins), 4) Contribution best practices, 5) Etiquette and reciprocity, 6) Tracking performance from group boards, 7) Creating your own group board, 8) Managing and moderating, 9) Risks and considerations, 10) Alternatives as group boards decline.