I was just wondering if anyone knows a more comfortable fingering for black-key glissandi. For descending (RH), I use the side of my index finger, and for descending, I drag my four fingers (palm down), but after a while this can make the joints hurt a bit. I was wondering if anyone knows a better fingering. (This is my first post, by the way.)

You said descending twice. I think you meant: index finger descending and four fingers (palm down) AScending. If so, I would say that four fingers (2-5) palm down are good for descending, and the same fingers (palm down) but fingers curled under, are good for ascending. Using these same fingers (maybe minus the 5th) is the only way I know to do a whole-tone ascending glissando (C,D,E, F#, G#, A#).

Welcome "Alkan-ator" <Said in English with German accent.>

Oops. I meant descending I use the side of my index finger, and ascending I use fingers 2-5. I find it just slightly less painful to play the descending ones with my index finger (hand turned sideways). My only real problem with playing with fingers 2-5 is when I am playing on pianos with sharper-edged keys and my finger-joints hook slightly on the sides of the keys as they pass over, which hurts after only a couple glissandi. ...Or is this issue for the most part unavoidable?
For the whole-tone glissando, do you move your hand forward and backward as you go up?