I always use bait, any sort of bait. I have a pocket on my jacket where i keep various types of bait (peppermint treats, grass, grain and a crinkly peice of paper). My horses know that when my hand is infront of them to be up and out and show.
You could try using a crinkly peice of paper or candy wrapper. I use that on some horses and really it does not distract other handlers or their horses, its subtle quite ..just enough for my horses go to "hey what is that?".
Will he show to hay ? Try that ...it can crinkle and make noise and also get his attention. I normally bait with grain or treats and i teach them at home (with show halter on) to show to that and if they start getting lippy and grabbing for the treat i give the lead a small yank.
So you can try other things to get his attention such as hay, crinkly wrappers ext.
ALSO ...
What you could try, get something scarry such as a plastic bag (My horses prefer Walmart bags
) of news paper and at home, put it infront of him so he arches his neck ext. Keep doing that and he should learn that when your hand is infront of him that he has to "show" ....that is somewhat what i do. ALSO, a little tip, i keep a peice of crinkly paper in my pocket that i cut from the INSIDE of my feed bag, that way it smells like the feed as well
.