What I've found after more tha a half-century of playing, is that the need for calluses is a function of poor left-hand technique. A long while back, I made a concerted effort to positrion my fingers close to the frets, and to see how little finger pressure would suffuce to produce clean notes. Result? No pain, virtually no calluses and much less tiring playing.

Works on steel-strung and nylob-strung guitars, as well as banjos and mandos.