Practice, practice and more practice...........This may sound wierd but relax your grip only a slight bit. If you grab too hard your hands will cramp up. I had this happen to me and I lessened up only slightly and it made a world of difference.
Actually, not a bad idea. I first used a bandana, it was soft enough and at the same time kept a better grip then manually. Now, I can grab more on the shaft than the glans when I do A-stretches or bundled blasters so using my hands is much easier, and no cramping up.