Just a confession: after 3 years using Nikon I still have troubles to unscrew the rear caps. Wrong direction and either way the caps (LF-1 as LF-4) are too tight or too lose. Sometimes I transport the stuff in a bike bag and if the rear caps are not tightend enough, they get loose after some bumps. Because I tightened them sometimes a bit too much, I had problems to unmount the caps, especially in a situation I would need a third hand.
Now, after discovering what Sigma did with their LCR NA II caps for the new lines of lenses and enjoying the smoothness of putting their caps on and off with only one hand necessary, I ordered for each lens a Sigma rear cap. After all they were not more expensive than the old Nikon LF-1 caps and it's great to use them. Why?
I can remove the cap by holding the lens and unscrewing the cap with my thumb and index finger and mount the uncovered lens to the camera in my other hand.
How did they do that?
Those three elements are designed like a spring. They grab the counter part of the lens' bayonet, but they don't need to be "screwed". They just stay in place with little physical effort. Nikon's caps are really stiff, therefore one needs to tighten them and because I still turn in the wrong direction when I want to remove the cap, I tighten them unwillingly again. That's not possible with the new Sigma caps.
And another habit I kept from those front caps with the slippery surfaces (to my fingertips): always when I buy a new lens I engrave some deep tracks into the handles of the front cap. I use long nose pliers with some teeth on them. Now the caps don't slip so easily off my fingers.