A large active downline is manageable while providing personal attention to everyone. Delegation is the keyword here. Team Leaders can play a vital role here. Team Leaders can help to oversee their respective downlines while you keep an eye on their progress.
Making use of communication tools like PSA mailers, Genealogy mailers etc. can provide the personal attention.
Making use of websites, blogs, weekly newsletters etc. is helpful in managing a large active downline.
