jimmy paige (along with many other rock guitarists) used the pinky for hte slide, for the main reason of that most solos he did werent chickin pickin slide guitar. it was usually a few smoothe slides and a lick, which didnt require as much control on the slide. bluegrass and bottleneck players usually use hte ring finger so they can play chords with it. i think it comes down to whether you play licks or chords with the slide. i play wiht the pinky, but i dont play slide much, so i dont really know much, apart for some delta blues **** and a few slide guitar solos.