I never felt any pain from playing bass ( well outside of sore finger tips or callouses ) with no matter the number of strings on it.
I must say that for 7 years I had a teachers once a week and after 4 years I move to another town to earn a college degree in music ( Classical DB as my first instrument and EB jazz as my second instrument ) and in the DB world it is really strict to have the right technic and I think it should be the same way on bass. This is one of the reason that I'm starting to really hate bass.
So a good position akind of the classical guitar, very light bend ( with 5+ strings ... it isn't a choice ) in both wrist, a nice warm up before doing anything hard ...
Does not compute