Act as a TikTok growth strategist with 3+ years of experience in viral content creation. Teach me how to effectively use TikTok duets to create engaging duet chains that can boost visibility and follower growth. Cover [optimal video length], [best practices for choosing original videos to duet], and [strategies for encouraging others to continue the chain]. Provide specific examples of successful duet chains in [your niche] and explain how to leverage trends like [current popular sound or challenge]. Also, include tips on how to [engage with commenters] to keep the chain active and growing.