There hasn’t been a brokered convention in the modern era of the primary system (post-1968). It would 100% be a circus. Good for TV, probably exciting, almost certainly bad for the party and its candidate. My guess would be that everything would be handled by the prospective nominees before the convention itself to avoid looking like a hot mess in front of the nation.
The West Wing had a brokered convention that went like seven ballots. Was a good episode IIRC.