I'm interested in doing something like this (not same topic, just structure). Could you share something about your approach to convince the founders and the technicalities of the interview process.
I don't think the founders (of small personal projects) need a lot of convincing, do they?
"Hey, I'm doing a book and would like to feature you. Do you have 15 minutes to answer 6 questions?" You're going to get a 90% hit rate for side-project founders I bet.
