How many mangakas use digital or traditional tools to make their manga? Do mangakas in Japan often make their manga using digital tools such as using a computer, wacom tablet, clip paint studio, etc, over using traditional methods such as using pencil, paper, inking pen, rulers, etc? 

What is the most used method to create a manga today in Japan?
From what I've seen, it is mainly the age of the mangaka that makes a difference: older mangaka stick to the traditional pencil paper, many of them young ones work quite a bit with digital. The rough copy with a pencil and the final drawings will be digital.