Aww, I actually like the thicker line most of the time! Since I like a thicker line on my lower lashline, I drag the pencil at an angle to sort of flatten it and it creates a bit of a point, which I then use for my upper lashline.
I think there are also sharpeners for these which resember a crayon sharpener. But I found that in a hurry, doing a couple of quick strokes at different angles on a piece of paper does the job too! HTHS!