I have two fully flighted birds inside my house and we just adjusted our home environment to make it safe for the birds. Delfin, whom we have had for over a year will fly to any of the family and sit on the shoulder and says "hello" then asks "what are you doing?". Delfin is part of our family and Mulawa is starting to realised that we are her flock now.
Delfin will step up and down, lift up one wing at a time for inspecting under the wing, come when called (unless eating) Shakes hands, turns around, lifts both his wings up and will pick up wooden beads and put them into a bin. This was done even though Delfin is fully flighted. Delfin has also been trained has to where he can and can't go.
I spend a lot of time training my Birds and have had no difficulty in training them. In fact because Delfin is trained it is easier to train Mulawa. She has been stepping up and down for a while now and she starting to shake hands. This has been my experience.
I suggest while he is sitting on your shoulder or head, very very slowly raise your hand with a spray of millet to him. has he becomes use to this procedure start to reduce the size of the millet until you're offering a cluster of millet between your fingers. I would do this before your birds mealtime.
I'm from Australia and yes the wild birds will take food from your hand.