Likely a matter of practice and muscle memory.
However, there are many variables and there certainly could be some combination of variables that simple make the process cumbersome and awkward for you.
Hand size being one, Finger joints, flexibility, etc.. Ergonomics.
For the most part you may need to do some experimenting to discover what, if anything, does work for you. And what works probably will involve some trade-off's.
I found a number of "Butter-fly click" links via a Google search. Explanations, videos, clicking speed tests, etc..
Not at all sure (full disclosure) how real and effective that all can be.
I am going to move this thread from "Computer Peripherals" to "PC Gaming" with the hope of soliciting further ideas and suggestions from the PC Gaming community and those who are more likely to use Butterfly clicking.