What Tool Can Grip Without Marring Finish?

I'm trying to remove an LDC from a shroud. The LDC unscrews but leaves its end cap with threads still on the shroud. I've tried gripping that end cap with a rubber pad used to remove stubborn lids from jars. No luck. This is not one of those epoxied permanent installs. I guess my finger tight twist was just a bit too much.

Any suggestions to get a better grip without marring anodized finish? I don't have a vise that I could line with rubber or leather.
 
Great ideas all thanks. For whatever reason after being stuck on for 5 days, I tried to remove by hand after shooting a 100 or so rounds and it just came right off without much effort. Really - no alcohol of any kind was involved. No clue. Just glad it came off without scratching anything up. Immediately lubed threads lightly on LDC parts and the shroud.