For me it was just a matter of interacting and being around them as much as possible. Make sure you respect their boundaries, so they know that you’re not a threat and aren’t forcing them to do anything they don’t want to. Just keep motivating them with the food and just generally keeping them company
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I think mine enjoyed spending time with me more when I actually made them work for treats, such as getting them to fly to me, go through my hands as a tunnel, spin etc. They also enjoy eating whole pieces of veg from my hands, it’s nice because it’s something different for them and they get excited because it’s normally different in their cage. I also play with them, so I hold their shredding toys in front of them outside the cage and they like playing with them with me.
I have 2 budgies now, and one that had passed, and they were/are tame to different extents. One gives me kisses and preens my face, one used to spend loads of time with me and sit on my head, one talks to me loads and enjoys being carried around everywhere. I think it all depends on their personality.
Good luck!