The procedure is basically using a collar on the donkey and hooking up the calf with a 3 foot rope to the collar via a strong rope. Turn them loose and let the donkey boss the calf around.
I have never liked this method for the same reasons I have never liked using a tractor, atv or other vehicle. The calf gets used to the donkey or vehicle but not a person, so while the calf may lead and behave with them, they will not necessarily lead and behave with a person. So, in my opinion, the process is pretty much worthless.
That being said, I know a lot of people use donkeys to "take the fight" out of them. And have success. So I guess it is a matter of method and opinion. I would just as soon work with the calf from day one and build a trusting relationship rather than start over at day 10 to build trust that was gained by a donkey!