If it's a garden-variety interview video, why not use 2 cameras and 2 mics(questions and answers on different cam)?
If the questions are off-cam/not important why bother with miking the interviewer?
If the questions are on cam/important and you are using only one camera, why not 'cheat' and record the interviewer angle after the actual interview? Then you only need 1 camera and 1 mic.
For single cam interview, begin with a mock establishment 2-shot with the interviewer introducing the guest.
On the same wide shot, ask the interviewer to ask one or two questions from the middle of his list. Finally, ask the interviewer to thank the guest.
You can then to proceed to change the lighting for the guest. Begin the actual interview. Advice the guest and interviewer against interjecting each other or cross-talking.
You can alternate between over the shoulder shots or close ups of the guest if you are alloed to pause the interview to change framing.
Otherwise, close-ups are easier for continuity in case the interviewer starts to vary hand positions/head angle/ body posture during the interview. Keep recording going even as the guest stops to listen or pause to think. These are cutaways.
After the final question has been answered, ask the guest to fake a few noddies (reverse/reaction shot to questions) just in case you need to cover jumpcuts for a stuttering interviewer.
Now for the interviewer angle, ask the guest to sit for a few over the shoulder shot of the interviewer. A few questions will do. No anwers needed obviously.
Thank the guest and walk him out.
Review the recorded footage with interviewer and note down the dynamics and questions asked.
For safety, reshoot all the questions including previously recorded over the shoulder and master shots incase the earlier cheatshots don't work well due to difference in postures. Make sure to obey the 180 degree rule and keep the shot size and eyeline for both the interviewer and guest roughly the same.
Fake plenty of noddies with different expressions for the interviewer.
These will come in useful when you need to truncate/clean-up the answers smoothly.