Here is what I found for an image of the bit you describe: That is the bit
Was the former bit all one piece? no 'break' in it, just a 'bar'? that would be called a 'mullen mouth' bit. Some horses really HATE the movement of a jointed bit and work better in a solid bit, like a mullen mouth snaffle, or a solid mouthpiece curb bit.
It was just a solid rubber piece with loose rings for bridle and reins to attach.
Once you DO get the bit in, how does he react to it? Is he irritable about it, and throwing his head up if there is any kind of pressure on the bit? That might indicate his need for dental vet attention.
The vet was out this past March to give a physical and administer any required vaccines to bring him up to date with the Vet. At that time, he also examined his teeth. He said it looked as if his teeth had previously received attention, within three maybe four months. He did not seem to find any sores in his mouth or physical/medical problems at the time and felt the horse was good to go.
As for making your own hands soft, are they hard? and if so, can you explain why? (I mean, what sort of riding past do you have ?)
It has been 40 years since I was on the back of any horse. My last horse was a paint and he was very ready for anything. He too was a really good horse. Getting him to stand was his biggest issue. He would dance constantly. We tried different saddles, blankets and anything else we could think of. I think that may be where I am fearful my hands may be hard. Because of the dancing, you were always having to rein him to stand or he would dance all around and cause others horses to become excited.
The horse sounds like a pretty solid citizen in all other ways, so please don't give up on this. IT is an eminantly curable problem.
He is a good horse and with a better rider/trainer, would become an excellent mount. I know it is curable and I really hope some of the suggestions here will help me to understand how to become a better teacher.
Make sure he has not mouth /teeth/cheek sores, his teeth are in good order. this must come FIRST!
His vet gave him a thumbs up.
Make sure you aren't placing the bit so high that it is gaggin him, or so low it is clanking his teeth.
I will get some pictures with the bit in, I only have one wrinkle at the corners and as I said before, sometimes he stands quietly with the bit and other times he seems to play with it.
Make sure you aren't clanking his teeth when you put in/take out (to the best of your ability)
Hard to do when he wants to giraffe away or toss his head.
Teach him to lower his head , doing the many times withough actually putting the bit in, and then doing the bit.
I think this is the most important piece. I don't think I have ever seen him lower his head for halter or bridle. He does not resist the halter but knows when he sees the bridle and bit
try wrapping a piece of fruit rollup candy around the metal bit when yoiu offer it to him.