Not a specific finger for doing it. However the common is the Ring or Middle. I personally use Ring.
Try multiple fingers, and whatever feels comfortable you should use. Cubers have different styles, just like painters do, making a masterpiece doesn't have to be accomplished by doing what everyone else does. The oddly styled ones are the ones who are remembered.
I have a question, why does the Jig-a-loo in my Zhanchi "dry" up so quickly? Like a freshly lubed Zhanchi feels super fast and very smooth, I can almost feel no resistance.
But after 2 days (I do about 20 solves a day) it starts to act a little funny. It is noticeably slower and I can tell because my algorithms are much "locky" and slower.
Is this normal, or am I just having problems?
Thanks.
While I sometimes use my index finger for an M move, I'm pretty certain that the index finger is NOT the standard finger that people use for all M slice moves.
It depends on whether you want to use your left hand for all U moves or not IMO. Because doing it both ways means your right hand now and then isn't available to do U after an R2.
If it is noticeably either way, turn it that way, then determine its +2 status. If it isn't noticeably either way, go with the benefit of the doubt and say no penalty.