existing sprinkles on Nostr: I think the problem is your lines are too thick so you can't build up the value. ...

I think the problem is your lines are too thick so you can't build up the value. Which gives you less control and ends up just being black. Try a thinner pen and try different pressure. I would just try making value swatches first. Something like this: https://helloartsy.com/crosshatching-value-scale-simple/