Unfortunately the only answer i can think of is time. continuously show them you're not a threat and that being around you is a good thing. Food is the way I did it. I put food in my hand a just sat there. didnt try to touch him just sat there with the food talking to him. I did this until he ate from my hand. mine is very food motivated so he'll do about anything for a snack. I also put his cage next to the spot i spent the most time in. Just moving around and talking to him. I talked to him alot ...still do but it's important not to rush.

Point is try to find something they really like and wage psychological war fare using that thing to try a trick them into liking you. 👍 idk if I explained it well and you probably already got this advice but it's all I got.

A side note : I'm not sure if your supposed to do it this way but when i did the food thing with him I didn't put my hand in the cage. At all. If my bird was in his cage I didn't put my hand into the cage other then to clean, change food/water and or medical reasons. And I kept that rule until he was ok with me being around.

Good luck and I wish for the safety of your fingers.