I think a german martingale would be a good tool. I still use draw reins on Ruger every now and then. I don't use tools like that in anything but snaffles to be honest.
Was going to ride today, but 10 degrees with a cold wind is a little too cold. We planned to haul to an indoor tomorrow afternoon, but a blizzard is supposed to be coming through. If the roads are bad, we aren't going.
I agree that Red is a green horse. He is sensitive. Some horses are just like that. Selena is not, Ruger is not, but I have worked with many a barrel horse that is. There is nothing wrong with a personality like that. You have to take into account what type of horse you are riding. Example, I could beat up on Selena all day and she won't panic, buck, jump, or anything. I am currently putting 30 days on a mare for a friend, and if I smacked her or pushed her around like I do Selena I'd be on my ass in the dirt in a heartbeat. For her, a simple hindquarter disengagement is devastating. For Selena, that's nothing.
My old horse Beau, if you needed to yank on him for something, he had forgotten about it 5 seconds later. No biggie.
Shotgun, my 2 yr old, if I need to get after him, he's back to being a "ho-hum nothing-bothers-me" after I correct him, like nothing happened in the first place. (Strange he's so laid back, because he's super bred to run barrels too.)
But Red? It's got to be presented in a calm, no stress method. No yanking. No yelling. Etc. He can't handle it.
Red is a horse who needs you to get inside his head IMO. Seeing as he is green(er), I would do a ton of small, perfect, flexed circles. Just something simple like that and demanding perfection. It doesn't have to be a huge production with him I suspect.
He is a GOOD horse. He's just requiring some special handling. Makes me think of a cardboard box that says "fragile, handle with care" on it, LOL.