cleaning up drawings

Hi there,
I’m borrowing a graphics tablet at the moment and it’s really good! Anyway when I draw with a real pencil on real paper i can scribble away to my hearts content until I get the shape i want (I can even draw some motion guides etc) and can then trace it on a light box to clean it up and get a sharp single line (which scans really nicely in to toon boom).

Using a tablet if i try to refine the line it seems to become a bit of a mess of black if I’m not careful. It seems a bit robotic to draw and rub out draw and rub out until I get the shape i want. Ive also tried drawing with a guides etc then going to the next frame tracing it to clean it up then deleating the messy frame but this isn’t ideal. Does anyone else have this probelm or does everyne else just draw ia nice single line first time?

I can do it using auto light. I don’t know why I didn’t see it before