Growing my userbase with niched newsletters

Today I'm trying to find ideas to grow my userbase.

I launched a product called unblokd.com where you can unblock your code or unblock others.

It's aimed at developers, at any stage in their learning.

My marketing efforts up until now boil down to posting about it everywhere and finding a simpler way to explain what it does to people. That worked well, I got quite a few users joining in, so it's promising. But it takes a lot of effort and stops when I stop posting.

So I'm looking into ways to make that work with less effort.

And right now I'm thinking of advertising it in micro-newsletters aimed at developers. I think that's a good way to reach a targeted audience. This week I'll be trying to find those newsletters and getting in touch with their authors to see if I can advertise and how much it would cost. I don't have a significant budget, so I'll probably be going for newsletters with smaller audiences (<5,000).

I knew there was a website that featured micro-newsletters. I'll try finding that and I'll share it here if I do. If anyone else knows any sources please share.

And I'm also curious to hear what others think of this strategy.