When first learning how to draw 40years ago, I used everything imaginable to smear and blend the graphite. Even though the results back then were satisfactory I learned that your artwork is much better rendered without the aid of such tools. Although the use of a paintbrush when blending hair comes in quite handy it does not give you that smeared look to a piece.
Darrel Tanks Five Pencil method is a great tool to learn from for blending with graphite.
I've tried the Five Pencil method back in school,but man am I lazy! Guess that's what got me down to one pencil. I have a book on Sketching at the telescope, And they use them a lot. That has got too be one of the most challenging things ever. Trying to pull detail out of something you can barley see. Dust lanes in galaxies light years away.