(Wall Street Journal) — For Shelley Davis, the secret to promoting a business on YouTube isn’t making videos. It’s talking to customers. Two years ago, Ms. Davis decided to set up a YouTube account to show videos about her hair-care company, Kinky-Curly Hair Products LLC. While poking around the site, she found that lots of African-American women had posted video blogs, or vlogs, about choosing natural hair over braids, perms or dreadlocks. This was right up Ms. Davis’s alley, so she jumped into the comments sections of the vlogs, offering advice and answering questions about her products. The result: a surge of support.