Two ways I do it. Lick your pointing finger and middle finger and wipe them on your slacks so they are just 'tacky'. Apply light pressure on the
jewel cap as you try to twist it off. Sometimes you may need to get your fingernails under the edge of the
jewel cap and pry up lightly to get it unjammed enough the unscrew it.
Lately, for difficult
jewel caps, I make a loop out a piece of scotch tape (sticky side out) around two fingers and that generally will grab the jewel cap.
One forum member used a Dremel tool to cut a small slot in the top of the Jewel cap so he could remove it easily with a coin. Bottom line, don't crank that sucker down.