Can I be the first to point out its both technique and practise.
From my notes this sleight took about two weeks to perfect (fit for purpose but could do better). From recollection, the most helpful
changes I made were a fresh deck, and correcting my finger position.
The best description of the sleight (for me) was from giobbi. Nip into your local magic dealer and take a peek (pun was intended).
I do own the superb Born To Perform but I do prefer to work from books for sleights, I'm just funny that way.
I can't remember if reducing the deck size was helpful, perhaps others can advise.