I did, in the early days of Uber (when we still had to explain what it is). It was also a time when in Switzerland the barrier was higher for people to start trusting an American app that asks for your credit card before you can even start using it. So we thought word-of-mouth through Ambassadors might work well.
We found them through social media and email outreach, offered them an individual invite code to Uber and free credits (for free rides) for each sign up that came in with their code. Additionally we organised small events where they were always invited to and they actually really got to know our small city team. I really enjoyed that program. It helped us a lot, but wasn't a big game changer in terms of sign ups (I should probably have scaled it more). One unexpected result was that it helped me get intros to awesome people and I could close a lot of partnerships because of it.
@sarahxjo Thank You for sharing your experiences. Correct, the goal at this time my team and I have in our minds is to introduce the product to a broader audience. The product is ProApp, with which we help people either start or switch their skill set to design. The niche would be the students in colleges pursuing design courses. Let me know if you have any more ideas on the same, happy to hear :)
I feel like the trickiest part is always: What can you offer to them in return? Of course they love your product, otherwise they wouldn't be power users and be talking about it already before being official ambassadors. So for me, the first step is thinking about what I can do for them to make them feel valued and to show appreciation for their work. Do you already have some power users and then maybe you can start from there?