Word-of-mouth leads in Detroit - what worked for you?

A friend who works at a local manufacturer says there are openings not advertised online. Any experience at all would help. They prefer people who can start within a couple of weeks. What do you write in a cold email?

A short email with two sentences about what you can do and your résumé attached worked for me. I followed up after a week.

Visiting in person worked for a trades job. For office jobs, email was better.