I guess you know him the best, but I feel like the best thing is to not assume he will be nervous. After all, it does appear that he has been out and about on a tourist visa for almost a year, LOL!
I put the chain over the nose if I think otherwise I would get turned into a ground pizza or the horse would get loose, otherwise I try to act like I think everything is going to go very well, LOL.
I don't know if you longe your horse but if he knows how and the show grounds has an area where that is allowed, sometimes that can be a good way to let them get the ants out of their pants, as long as they are under a modicum of control and won't disturb anyone else or get hurt. Some of the horses, after having a chance to move freely and neigh as much as they want, they then settle down. That or a long ride in the warmup area. Some get better if allowed to get it out of their system, and some, it just makes them more frantic, kind of like a tired toddler, lol.