Once you’ve gathered a list, put together a template outreach email (as you’ll be doing this over and over) that’s short and clear with expectations. Tell your potential interviewee who you are, what your podcast is about, and what you’re asking of them. Do a few test interviews with friends and family to make sure everything is being recorded at the quality you want and then book your first episode.
If you have pop-ups and optins on every page, I would have to think that it would be a lot harder to convince someone to link to it. Especially since the pages where you have your optins (and probably receive the most traffic) are probably the same pages that you have your best content on as well that you'd be hoping to pitch in your outreach campaign.