What is the best way to pitch for Beta Testing?

I would like to know your opinion on pitching users for beta testing. We are very early for this, but thought of starting little early. Do you ave some best way for pitching developers and agencies? We are a team of 4 people our of which 3 are developers and myself into product management and research. We are completely self funded. We crossed half way in developing a API first multi channel content management. There is already a market and users and competition also. Comparing to the existing players we offer many unique features, this is a not a statement but we designed the whole system by doing a extensive market study. We plan to launch by next summer and start with a closed beta. Our product is primarily targeting developers, agencies and enterprises who have own development team for their digital experience. What we thought is to give discounts for all our products for beta testers for their involvement for lifetime. Would like to know about offering discounts, whether it will look bad? As we are self funded, we thought it might be the best way to manage getting beta users. I had already listed many community groups, twitter, reddit, slack, linkedin and gitter but like to get some advise on how to pitch. Do i need to pitch with our product first or to ask for time to explain it deeper? Do i need to have an in-depth details ? As the user community are developers will it be ideal to ask them to look into the app itself after giving them the brief? Pitching with offering discounts is good or bad? It will great if i can get some advise on the above things