How do you clean up a noisy remote guest and balance two hosts in Reaper

[MichaelL]

I'm mixing a podcast for a client that features two hosts and a remote guest, and I'm struggling to get a clean, professional sound. The host tracks are decent, but the guest's audio is tinny with background noise, and when I try to EQ and compress everything to sit together, it either sounds over-processed or the levels are still unbalanced. For audio engineers who work on spoken word, what's your step-by-step approach to cleaning up problematic recordings and achieving a cohesive mix? Specifically, what audio mixing techniques do you use for noise reduction without making voices sound artificial, and how do you handle sidechain compression or volume automation to prevent the hosts from talking over each other? I'm working in Reaper but am open to general workflow advice.