I am and was the second owners of my greys too.
My Timneh -now an angel - was really tame, knew to step up, to fly, let me to pet him, loved playing with toys, everything. His first owner had raised him as the perfect bird.
I own a Congo now. When he came to me, he didn't know to step up, didn't know to fly, hated toys, hated bathing, never went out of his cage for two years etc. Now, his feathers are growing back, and the succeded two flights! Now, he doesn't love toys yet, but, after a week, he starts to play with it. Now, he loves to bath! He really does

In his first days, he didn't even wanna come out of his cage. Now, he goes out his cage, and walks in the room. My Congo loves to cuddle, and talks too. These are the good ones. But, it's been eight months and still won't step up for me. I tried target training, step-back, putting my hand in front of his chest, stepping on stick-then my hand-.. etc. But, none of them was successful. He just doesn't get that I want him on my hand. Sometimes, I feel just like you do. "he will never step up or fully bond with me." I know that every bird can be trained, I trained 14-15 myself, but he's being so challenging. Any tips?