ive been doing pandora for nearly a year now- still not as smooth as Mr.Lapping's but ive got the handling down nonetheless.
Just keep practicing. do it slow and work towards smoothness.
im practicing B4 as well by Andrei jikh, the hard part isnt the Thumb balance as what 99% of the people in the forums would say, it would be the extension packet that extends from your packet hand to your performing hand which ****s it up for me- cause it falls off.
not always, but most of the time it does. just needs more practice.