Friend of friend trained his, I am gonna try to find out for you as I know he was taking some kind of course, but as DizzyBlue said you need lots of bonding and indoor flying training, harness training is great idea ( I think that’s how my friend’s friend was starting with his parrot) you don’t know how your parrot will react to outdoors ( and you don’t know how he will react to harness itself, especially that you can’t just put harness on parrot he needs to get used to it) I don’t have macaw and my parrots don’t free fly but when weather is nice I take them to the garden in travel cages…looking on my 2 indian ringnecks, we got Blu in winter so I had plenty of time to build some bond with her, teach her few things and it was never an issue to get her into travel cage and sit for a bit in the garden, then we adopted another ringneck last July so for me it was obvious it’s nice weather we are going out… but she hated it in fact first few times she wouldn’t even move in her travel cage but I thought she will get used to it… well she didn’t instead she started screaming and just pacing, so I screwed up the whole experience for her, because I was stubborn and assumed she will understand my reason for taking her outside… so in the end I stopped taking her outside and went back to basics and it’s fine now she doesn’t mind but still I don’t take her out for long periods of time, looking from perspective I still feel kind of ashamed of myself as taking into account all I knew about Bluey I shouldn’t push on her when I did, we didn’t have much relationship, she didn’t understand why she couldn’t be at her old house, everything was new and then I was tricking her into travel cage and taking to unknown simply instead of creating enjoyable time I stressed her, once we took step back things got much better… in general with Bluey it was lots of taking step back.., she screamed like mad for many months… now I think she got better or we got used to it…but I didn’t have crazy screaming for long time since ages when few months back she could scream for 5 hours straight for reasons I never figured( we figured few but not all) just one day she sat in her usual screaming spot but started to talk instead of screaming…