There are a lot of advice out there for this, only that it is always for full-time endeavors, ambitious startups with a team of co-founders and even hire market

There are a lot of advice out there for this, only that it is always for full-time endeavors, ambitious startups with a team of co-founders and even hire marketers. These advice can give insights but are rarely directly appliable to side-projects. What you want is a constant, predictable source of people genuinely interested in your project, rather than growth hacking your way to the exponential explosion. The best way to do it for a side-project is to have access to and trust from an audience. There are two ways to do it. Write a blog and be part of an online community where your target audience hang out. That is why the advice of having experience at the industry you are focusing is even more a sine qua non than with startups. Both actions are actually very complementary. Regularly write interesting posts on your blog and create an audience with time. Regularly contribute at HN or subreddits or Twitter or whatever and gain trust. In both strategies be sure to be useful and deliver value not necessarily related to your side-project. If people sense you are only doing that artificially as pure content marketing, you will lose their trust. And for one-man side-projects, this kind of trust it is even more important than to startups.