I use a heavy, acid free Cartridge paper. Pretty much standard for anything artists use for drawing. The only thing I do differently is that I work on the back of the paper because I don't like the tiny ripples on the front.
I don't like my paper dictating how my pencil interacts with the surface.
This picture is truly amazing, I felt lucky to find a picture that resembled Clint in an artistic way, because most of Clint pictures in DA are photographs or photo-manipulations, so I'm proud of you for making great composition with no more than ten colors, the only thing I don't like are the red letters and the Japanese signs because it ruins the picture essence, but anyway I love the drawing! Cheers my friend