BirdManDan
I do agree that positive re-enforcement, touch and clicker training are the go when you have birds that are cage- bound due to aggression. Personally I wouldn't let that type of bird out of it's cage until it was adequately touch trained. However with that said, there are some birds who will happily take a treat from a hand while in a cage or on a stand, but will bite if asked to step up, especially from within a cage. There is also birds who will happily step up onto a hand and then reach down and bite a finger. I believe this is from learnt bad behaviour. So while the bird is not lunging, it's still biting when attempts to have it step up or after it has stepped up.
If the bird needs to be moved to another area, then the choices a person has, is to grab the bird and get bitten, towel the bird and get bitten and destroy any trust, ask the bird to step up and get bitten, hope that the bird will go to where the person want's it to go to, ( doubtful) or use a T-perch. I found that a T-perch is better than a stick. The bird can run down a stick and bite the hand. But with the T-perch the bird can run from end to end but the hand is out of reach.
Birds use their beaks like a third hand and they will use this "third hand to help them onto your hand when you are start the training of step up. This is because the bird is unsure how stable your hand is so they test your hands stability with their third hand before stepping up.
This scenario happens when an inexperienced owner is not clear in their signals to the parrot. For example, when offering a hand for the bird to step up, an inexperienced owner often isn't quite sure of him/herself... so their hand motion is uncertain. The bird may wish very much to climb on, but is unsure of the stability of the hand will reaches with its beak (The beak functions as a third hand) to steady the human hand. The human, afraid of that beak, pulls their hand away. Now the bird is confused!
Now each time the human's hand is offered, and the bird attempts to grab the hand with its beak to hold it steady so it can climb on. The human jerks their hand away. The bird has no idea what has happened but if the scene is repeated (as it usually is), the bird will learn that it's beak will make the hand go away. The bird doesn't really want the hand to go away, but it is fun to control one's human's hand so the behaviour will happen again and a-gain. Once again, the parrot has no idea it has done anything wrong. This becomes learnt bad behaviour and they will actively hunt out skin to play this wonderful game of entertainment.
I think that people should use whatever method that works for them to achieve the end results. So if that means using a T-perch then that's the way to go for them.