When I lived in Chicago I bought a pair of leather gloves that were just a wee bit small and stretched them. With the gloves snug around my fingers I could operate a camera. These days I use full finger mountain biking gloves that make it easy to use the controls without bare skin and the slight padding on the inside of the glove insulates against the cold metal in cameras and tripods. I cover them with another glove or mitten. That works fine too.
I have to admit, I would prefer using hand warmers but I never know when I am going to go out. I prefer to keep things as simple as possible too.