Ask HN: How did you grow your side hustle as a technical (non-marketer) person?

For a side hustle, I built an app to track the rankings, ratings and reviews of my wife's books on Amazon. There was some interest from her author friends, so we decided to brand the product and make it publicly/commercially available.

The products is ticking along and the authors we've onboarded are happy. We need to onboard some more in order to break even. My wife and I have done some social and SEO stuff to boost the visibility of the product, but it's not our area of expertise (or interest) and it feels like it's going slow.

We've got some feedback on features our authors would like added, but I'm hesitant to invest more development time without growing the user base and pushing past break even.

For those non-marketers with a successful side hustle, did you roll up your sleeves and get the marketing done yourself or did you find some help? If you found help, what help did you get and how did you go about getting it? Or did you let word of mouth do the marketing for you and stay focused on building out the features your customers were asking for?