Are we talking guitar? Because if we're talking guitar then it's all about thumb placement. Thumb print on the arch of the neck should help with getting cleaner barres.
Source: Am guitar teacher
I agree. It also helped me when I finally got the funny skin on my fingertips, but that just takes time i guess
F shape barre chords are the hardest for me, but I've gotten the hang of just doing them with my thumb over the top instead of forming a proper bar