We're doing everything ourselves now, and it's taking more time every week. We'll see how things evolve, but since we're only two devs, we might have to do something about that at some point.
One thing that helped a somewhat was to send them promo codes directly.
It's a painful task, sending all those emails and keeping track of those who replied, ignored, bounced back, etc... :)
What app did you guys release?
Good luck to you!
We launched a little travel magazine; www.overnightbuses.com
Good luck to you guys as well!