How to turn HN users into consistent marketing channel?

My growth has stagnated qutie significantly after a really promising launch a few months ago.

The best performing channel by far during the launch was Hackernews, and after talking to a bunch of my premium users, I have a good idea of the type of person my product appeals to. These people frequent HN.

So I have identified where my users are. But I'm having trouble turning it into a consistent marketing channel, and was wondering if anyone had any tips for this, or for where else to find this type of person.

In general, it's been much harder than anticipated to get a consistent, working marketing channel. I'm trying to hang in there, but I'm getting worried that the post-launch fade-away is real