One thing I miss very much from Leicas and other rangefinders lenses is the presence of the focusing tab. With a focusing tab, you can learn the focusing distance / position of a lens and get a feel for the distance and also making precise fine-tune possible with the slight move of a finger. There has been a few excellent commercial products made available, one of them being TAAB, and other various 3D printed solutions available, though in my opinion they all take away from the compactness of the X100 cameras. With the extra Sugru I had left over from dustproofing the viewfinder, I opted to make a focusing tab on the ring of the X100F.
The biggest gripe I have with the focusing ring of the X100 is that it's very difficult to turn without moving my elbow, because clamping onto the focusing ring and turning the ring just with my fingers without moving my arms is actually a very difficult thing to do. It's instead much easier to pull my left index finger back and forth, creating a very stable stance to eliminate motion blur.
I've experimented with different types of focusing tab, and I find the single hump to be the best for a focusing ring this thin. I've tried the concave arch as well as double hump and they're either too ugly or not strong enough to be useful. As you can see from the title image, I've decided to use the triangle shape to create a larger area for surface contact. As with all things Sugru, don't rub it into any crevices, try your best to leave it together in one piece. PROTIP: You can use the plastic packet the Sugru comes in as a makeshift knife for cutting and trimming off excess Sugru.
To get the most out of the focus ring, make sure your AF+MF setting is on. What it does is that once the focus is locked using AF, you can then move the ring to fine-tune it.