I've played almost 25 years, including some professional.

To answer you... I don't come up with fingering. I just do what my hands do. The fingerings in printed music are guidelines for pedagogy.

Honestly I'm not even sure I explicitly practice fingering. It's just repetition. I frequently think I change it though.

That being said as someone whos played so long it's like an extension of my arm, don't take my word for it. Experts are notoriously bad at explaining their techniques. I do think it's just practice though. No secret