As for callouses.... I don't really have them anymore. My fretting fingers are nearly the same as my picking fingers; old and crusty. Ha ha But for real, any callouses I had, I lost eons ago.
I played electric guitar for an hour and then bass for nearly 3 hours and these puppies are stinging now. I think I'm just short of getting at least one blister from sliding on the bass. Think I'll give them a day to heal and play some drums.