My ex was in another state and attended via teleconference. He and his lawyer (who was there in person) were in one room and I was in another. The mediator went back and forth.
One thing that helped me focus during mediation and the trial (we agreed on everything except sobriety monitoring and went to court over that) was to have a notebook and pen. I wrote down all the lies to keep track of them and conferred with my lawyer about the best way to address them. Sometimes it's best to let them just keep talking. My ex and his wife did more harm than good with their testimonies, so that worked in my favor. I know it's hard when the emotions are high. Sending strength your way. You can do this.