I admit it, I am vain enough that I did a Google search on "thinking with my fingers", to see if there were people I didn't know of who had linked to my site. And yes, there were, and some links which left me very flattered. The search however brought up a whole lot of other uses of the phrase, and most of them were - excuses. A very common one was like this: "I am sorry, I am tired, I guess I am just thinking with my fingers." Only at one point did a site on journalism and writing point out that thinking with your fingers means thinking while you write, something all journalists should do. I mean, it certainly beats thinking after you have finished the part and passed the writing on to the desk for editing and printing!
Then there were the musicians, describing how their fingers would have to do the thinking at a certain point in a performance, how technique and practice would lead to the conscious mind not being occupied with what the fingers did, and the fingers thinking on their own, and a few other technicians and artists also mentioning how their fingers would come up with solutions seemingly independent of the brain.
The last quote however gave a totally new twist to the term. Google, despite me asking it to search for the exact phrase, insisted on searching for thinking .... my fingers. While this lead me to the Isaac Asimov quote further down, it also brought me this: "Then you get another hard-on thinking about my fingers."