The article suggests doing a search for potential companies, finding contacts on linkedin, and sending out some emails. But what about experimental technologies or developer tools? I wouldn't expect a lot of success with a slow moving Fortune 1000 company in my city, and there's no way to search "startups using x" for a generic technology, like serverless or NoSQL.
I have found a little success going to meetups and talking in person to other developers and entrepreneurs, so maybe I need to more aggressively take this route. The internet is too big/impersonal/oversaturated from what I can tell.
What would really be helpful as a software engineer is a guide on how to improve entrepreneurial networking, which has to be the foundation before tackling some of the techniques in this article.