I do not prick my underneath finger, I simply feel for the needle to ensure it is going through all 3 layers. This usually involves scraping the needle on the pad of my index finger. I do have a callous but really not much more then a bit of skin that is slightly harder and not quite as sensitive as my other fingers. I do occasionally prick my finger but try not to make a habit of it. So there is no pain or fatigue involved with my underneath hand. Additionally I also sometimes use my underneath finger to create a tiny little hump that I pinch with my above finger to push the needle through to create my stitches. An excellent book is The Essential Quilter. Can be found on Amazon.
Many people can handquilt without feeling the needle on their underneath hand. I am not one of them. The ones that don't need to feel the needle have used leather thimbles, bandaids, liquid skin, a layer of superglue, the rubber finger toppers that bank tellers used to use, and a vast array of other items to protect their underneath hand. I have been quilting for around 20 years and never found the need for underneath hand protection. I quilt in a 14" lap hoop, not a frame.