Ah! I know EXACTLY your problem!
I guess your brush strokes look like this:
But you want them to be like this:
You must calibrate your brush pressure through the brush tracker. It’s more important than you first might think. Then also, velocity i also important when it comes to brushstrokes, I’ve notice that you can easier get a better transition of the brush size depending on how the velocity settings are set to.
Myself, I don’t use the cover pencil for lineart. I use a slightly custom made pen brush. Here’s a screenshot over the settings for my lineart brush:
If you have Corel Painter 12, you can give your brushes their own “brush tracking” settings, this is the calibration settings for my own brush. I think this is the most important thing you should know. And you can set these manually if you want to for any brush, really.
here’s how the Dab profile settings are set to.
And this is the size settings. If I’m gonna do some thicker kind of lineart, I set min size on 5-10% since otherwise it can give some way too thin lines at the ends. But if you are gonna use a pretty small size like 1 or 2px, then 2-4% min size should work fine.
I hope this helps you out!