Timber and I have been progressing very well and it turns out that he loves scratches. Last night, I was scratching under his beak and he started "beaking" my hand. He was rubbing it with his beak and pinching very gently (no pain). He put my finger in his beak but didn't bite down, just kind of rubbed back and forth.
A couple of nights ago I thought he was going to regurg on me, so I immediately put him back on his cage door.
I'm careful to only scratch around his head, and I do NOT want him to think I am his mate. Any suggestions? If he is just exploring my hand and being affectionate, that's great.