I was told that was his nature so XD;;
IT SMEARS!! XDD OH TRUST ME, IT SMEARS!! It's good to keep a scrap paper under your hand/wrist while it's sliding across the paper. Also, you should start from one corner and work your way across to the other so you're not sliding back and forth on it a lot.
And if all else fails, get a clean eraser. XD I smudge it up a lot too sometimes, so an eraser helps me clean it, lighten it up, and even add highlights c: Hope I helped!