I think you need to approach specific users (like forum moderators or reviewers of similar app) and share your app details. If they like they will respond to your app otherwise not. And also promoting in app specific places is good. For ex, xda, reddit's android subreddit where app can get noticed more quickly than posting it HN, where users have different interests.

Few days back, I posted a new app (that allows you to run mobile apps from sdcard.) which gained more comments and feedback on android specific subreddit more than HN. So narrow down to specific group or even individuals is one of the option.