Word-of-mouth leads in Phoenix

Two small Phoenix employers told me they are hiring but have not posted yet. I have been trying to stay organised about it. 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.