Our company has a new App Submission/Promotion/Reporting Tool for Android developers. It's free and we don't take any share of dev revenue. We believe in supporting independent developers the best way we can and actually we're trying to find ways to get in front of developers to discuss our product and hopefully get them on the platform.
You should be trying *everything.* Tactics I recommend include:
Looking at recently funded companies on AngelList, finding their Android engineer on the team page and reaching-out directly via email.
Using LinkedIn's advanced search to find Android engineers and getting a pro account to send inmail.
Twitter ads targeting people who follow Android developer related accounts.
Posting on HackerNews for feedback.
Happy to talk through all of this and more in a call.