In summary
When it comes to analysing user or expert interviews, I like these approaches:
Line-by-line coding when it's a complex and touchy topic
Multiple summaries: write summaries during and right after the interview
Workshop format: use silent and solo brainstorming instead of classical interviews and make the participants group the learnings by categorises
Line-by-line coding
In a sort of simplified Grounded Theory way, I analyse the text one line after the other and tag each part with the learnings that come out of it using a tool like Dovetail or Notion. That takes a shitload of time but also leads to the most in-depth learning. If you are interested in learning this approach in depth, the book Doing Qualitative Research by David Silverman is a gold mine.
Multiple summaries
Right after the interview, I summarise the top 3-5 elements that stick with me. After a few interviews, I summarise what sticks for me about these interviews. At the end of the process, I already have everything in the summaries, and if I have a doubt, I can go back to my notes. That's definitely quicker than the line-by-line coding approach.
Workshop format
The quickest way to do it, which I want to use more in the future, is to do the interviews in a workshop-like format with silence and solo work, and then group work where participants summarise the key topics they have in common.
Basically, my role here is to create a set of exercises that make people do my analysis work together. That's the fastest way of doing it, but the danger of "groupthink" is higher, even if the process starts with solo work.