When your product is publicly available (not clear from your website, given the signup barrier), you should do a Show HN. I'm happy to help you if you send a draft to hn@ycombinator.com—same offer goes for anyone—as long as you don't mind dealing with my terrible worst-case latency.

It's good to follow the tips we give to YC startups launching on HN: https://news.ycombinator.com/yli.html. The logistical aspects there don't apply to non-YC startups but the communication aspects apply to everyone.