Check out grippermania.com. They will tell you about niceties like setting the "dog leg" into the thumb side of your palm, and there's all kinds of grip info there. I also did some posts on contrast baths and other things that were very detailed on
www.dragondoor.com, which you can find if you do a search on them for contrast baths or grippers.
And re callouses, they don't have to get gargantuan if you file away at them regularly. But if you want perfectly smooth hands, that's going to be a tough order of course.