u/Guitar-Pick

Hey! Looking for advice concerning eyebrows; How does one thin out their brows without absolutely obliterating them or shaving them off completely?
Most tutorials I see online just shave off the tail or shave them off entirely.
I'm looking to thin them out without doing that.
Is there such a thing as shaving them on their thickness? If so, is it better to shave on the underside or the topside?

I have bushy dark brown brows, they're straight and close to my eyes (F).