My STBX refuses to talk and even try to go the uncontested route, is requiring formal discovery, is attempting to file temporary restraining orders (on false grounds so I'm not worried), and is demanding attorney assisted mediation. So to paint a picture, she's not very amenable and I don't picture her compromising much. I'm hoping (probably falsely) her lawyer has at least some sense of reason.

Yes I have a lawyer already.

Any tips for how to prepare for meditation, particularly an attorney assisted one? I'm honestly not quite sure on the details of how the attorneys will assist yet since the mediator was just chosen. Since the state of Missouri typically requires mediation be attempted prior to court anyway I may as well try to make it productive. I don't want to spend an extra several thousand on multiple rounds of meditation to get nowhere because I'm ignorant of the process and unprepared.

TL;DR - What advice would you give going into attorney assisted mediation? What was your process like?

EDIT: We have 1 child. Disagree on some logistics like 2-2-5 vs 2-2-3, but we at least agree on 50/50 since she realized she had 0 chance of getting full custody.