You find some people in your city who used to work in China, talk to them, hear how hard sourcing and quality control was and probably give up. Or you find those people on LinkedIn but this stuff is hard for people who really understand China. Making the right connections is hard, staying on top of communications is hard, quality control is comically hard.
It depends on the product. In general, you can either do it yourself, contract out sub-assemblies and perform final assembly, or give it to a factory with related experience and have them execute. With simple products like this, you are better off taking option #3 .. it saves a lot of overhead with respect to legals, financials, setup, etc.
