You’ve got to become an ad-hoc subject matter expert in many different areas, or be able to find and hire those people. This is everything from electrical, RF, design for manufacturing, mold design, packaging, logistics etc.
In my experience finding a manufacturing partner is a challenge, big ones are usually not interested in a low volume product taking up their assembly line space. They’ll usually want some contractual guarantees about the number of units and it’s going to make your eyes bulge the first time you see it.
Call a lot of people, ask a lot of questions, and get introductions from every possible person you can. A lot of manufacturing is old school business and relies on past experience and transitive trust to start a relationship.
I really loved the challenge, but this kind of thing is not something to step into lightly.