Occasionally, Hahn's even though they are weaned can revert a little bit when they arrive at their new home. We experienced this with Paddington and I know Joanna experienced it a little with Mia, too. We ended up spoon feeding Paddington bird formula a couple of times a day for a month or two and occasionally every other day or so for a month or two after that. He has not begged for a hand feeding for a long time now. The last time was when we was just getting some red on his wings.
It's usually a good idea to at least know where to get formula and a syringe, just in case and also to offer warm comfort foods such as cooked sweet potato, oatmeal, etc just in case for when they are settling in.