Time is what it needs. Handle in short sessions, 2x a week and not on the day before feeding unless you have to (Prevent your hand from being mistaken for food) and not 48 hours after feeding. And not back to back handling days. I handle mine when he was hissing and pissed at me by blocking his view using his plastic hide (6 inch flower dish) so he can't see me picking him up. Over time, once he feels comfortable enough, you can go without blocking his view. Don't loom over him or get him from the top. Go from the side.

It took about 2 months until Banana is comfortable with me so I can go and pick him up without any hissing or issues. Now it has been almost 10 months, he trusts me enough where I can pet his head for a few seconds.