You can build up a temporary callus with crazy glue but it will reduce the feel. (both good and bad) Paint each fingertip but for God's sake don't let them touch anything, especially each other until it dries. It should only take a few minutes. Then use sandpaper to adjust (or remove) the glue as needed. This will also help chapped fingertips and hangnails allowing you to play with a bit more comfort.
Doctors and hospitals now sometimes use crazy glue to close cuts rather than stitching so I guess it must be safe enough.