Hello Tony!
A big warm welcome to Purrs to you and Buddy, who sounds like an amazing dog.
Poor george. Hard to know what may have led to his lack of trust, but how lovely that in his way, he trusts you.
The training you and Buddy are doing sounds great, and I hope that you'll be able to find a cat who is happy to work with you, maybe through some of your contacts in the area. It made me smile, because I remember when we first oved to the house we're in now, we had tess (a beardie cross) and Paddy - back then a mature 8/9 year old ginger and white tabby. They got along so well together. Well, Paddy had been wanting to be out for a number of days, but being new to the area we weren't confident about letting him out, but the first thing we did was put the flap in the front door, and afetr a week, we let him out for a wander. trouble is, he stayed out all night (it was summer and he was in his element). I was beside myself with worry the following morning when e wasn't in.
Anyway, OH decided to go out with Tess, and see if Tess could find him. And guess what? She did! She located him partway down the big field to the back of the house, where he was investigating a large cherry tree, chilling out in the branches, where he got a bird's eye view of his new territory.
I wish you and Buddy (and George too) every success in your endeavours. Keep us posted as to how you get on, and meantime, enjoy having a look around Purrs.