I had to talk to a coworker who had this excellent idea, but either didn't realize it or didn't know how to "sell" it. So I told her, "this idea is great becaus

I had to talk to a coworker who had this excellent idea, but either didn't realize it or didn't know how to "sell" it. So I told her, "this idea is great because of X and Y, and I want to help you develop it". She thought about it and agreed with me. So here we are trying to carry it forward! I think you have to consider if your project is good enough for your friend to drop his work and come help you. And then consider if you can actually find the words that make him feel like that. But focus on enthusiasm and above all, honesty :)