How do you search for subsidiaries and sister companies from a master customer list?

A manual-first approach works best: start by normalizing the parent company names, then use LinkedIn and company websites to manually map subsidiaries or sister brands, and only after that apply automation for enrichment. Pure automation tends to miss relationships or pull in noise. You can also use tools like HG Insights to generate initial lists, though you'll need to handle name matching issues when removing existing customers since company names often don't match exactly.