I can't draw. Any "visual aids" I provide look suitable for a preschooler. An inept preschooler.
I cannot sustain an accent not my own for more than about half a second. Tops. I can muster some characterization in spite of that, but my range is limited, and anything more than "the players can tell when I'm talking as GM from when I'm talking as a character" is gravy.
My brain doesn't work in a way that lets me take notes while I'm GMing. At least not notes that are coherent or even useful later. Fortunately, my wife takes good notes in-session.