Maybe I'm doing wrong, but when I want to assign a material to some faces of my objects before rending, all I do is constantly moving the mouse between the material I want to drag it onto the face I want it on. And repeat. And repeat.
There really should be a way to allow the selection of multiple faces and then assigning a material.
What would also work would be:
Right-Click the material to select "material painter". The material now "sticks" and successive left-clicks assign it to the face/body which gets highlighted just as with drag&drop. When the user right-clicks the next time, the tool is reverted to the main cursor.