Our Eclectus Frankie was a feather plucker before he joined us. His wings were fine, but he had removed a lot of the top feathers from his body, leaving only the grey downy feathers, and his tail feathers are in poor condition yet he still manages to fly okay. We believe that he never had a bath/shower with his previous carers, so we give him a very fine misting every day - just a couple of squirts on each side of his body, under-side and top-side. He didn't like it at first, but it is very quick and he is used to it now. This encourages him to preen, his feather condition has improved as much as it can and he is no longer plucking. He is dropping a few feathers now, so we think that he might enter a moult soon. Aloe vera is often recommended for the moulting phase as it reduces irritation where the new feathers come through. Pure Aloe Vera Juice Organic was recommended from a UK supplier Fushi, but the same or similar product will be available in NL, and a pharmacy may be able to help if you struggle to find it.The only thing he did with his feathers at our home is preening. We saw him go nuts with his head on his anal region and then clean all his feathers which makes me believe he is using that oilgland they have there to just clean himself.
You found Tommy in less than ideal conditions, but it does appear that he had quite a lot of human interaction at his previous home (Post #77), as he is adjusting very quickly - a week is no time at all. It all looks very good for the future.