Webinar where I am the MC

Welcome to the Zoom Community, @TGAoW.

It's not as difficult as you might think.  You are the host, the creator of the Webinar.  You can invite someone (or several people) as Panelists, and once they've arrived in your Webinar, just make them a Co-Host, and they have all the privileges you have as a host (almost).  If you don't want them to have that much authority, just leave them as Panelist.

Now to make the view for the attendees look the way you want it... Spotlight the main speaker/Panelist and set the Attendee View to Speaker.  As the next speaker is ready to speak, either use the Replace Spotlight, or first remove the spotlight and Add the next speaker's spotlight.  This approach puts ONLY the Spotlighted person (or people) in the screen view of the attendees.  Don't be confused by your own screen's appearance!  If you have this set properly, the attendees will see just the special guest and their screen sharing, if active.

I always find it helpful to have another account (it can be a Basic account) register and attend the meeting as an Attendee on another computer in my office.  This way, I know exactly what the attendees are seeing.

Another recommendation: Set up a "test" webinar and practice, practice, practice.  After you've done it a few times, it'll be a natural process for you.