For Part-Time Creators, the ultimate source of synergy with the day job is expertise. Expertise is specific and tacit knowledge. Everything that cannot be taught: all the judgment you hone by doing, all the untold stories and relevant data recalled at your fingertips. Your work history will also give you credibility, although you must not over-represent what you can speak to.
If you can deliver your expertise concisely, you are now a viable consultant.
If you can package it into a repeatable process, you have a productized service.
If you can create something valuable disconnected from your time, you now have a product.
Talks about a creator middle class too, which I guess is kinda interesting