I'm not the most experienced here, but this is what I've done for mine.
Incidentally, how big is this BP?
My shy ones seemed to snap out of it by 300-400g without intervention so far and behave more calmly.
But when I handled them, I was calm but deliberate about picking up. When possible, I reached from the side or behind them. Once in hand, most of mine reflexively ball up, and I just hold them cupped between my hands like a small, dark hide until I feel them relax or they decide to push out of my fingers (or if it's been 5 minutes or so without change in body tenseness, I'll just set them back down for the day).
Alternatively, I set them on my lap and cover lightly with a blanket and set my hands around their body for security for 5-10 minutes. Eventually they learn my smell or get more comfortable and start poking out from under it to explore and seem less scared.
A few weeks of 2 or 3 times a week seems to be all mine have needed, but none of mine were quite to the tail-wagging state. (I did get two that were strikey with poor aim, no landed tags, that this helped out nicely, though)
Sent from my SM-G950U using Tapatalk