How do i use a thin and cleaner looking outline, AND be able to color it in more efficiently? I have a 2 pixel brush with a 2 pixel dual brush set to overlay to make it sharper, and while it does look good, i can't fill it in as well as i can a 4 pixel brush with a 4 pixel dual brush overlay
Like, here's an example of the brush i whipped up with a quick doodle using my touch pad

Looks good, but when i go to color it in on a layer below the lineart...

You can see a lot of the coloring spilling outside of the drawing, and the brush isn't opaque enough to hide parts the fill can doesn't fill in

Which means i'd have to fill in where the fill can can't, and that would seem unnecessarily time consuming when there might be a better way of doing this
A similar thing happens with the 4 pixel brush, but it's not apparent nor a problem i have to correct because the brush is too thick and opaque

And here are the bucket settings for the 4 pixel brush

...and the settings for the 2 pixel brush

The tolerance setting for both brushes is one value before fill color takes over the entire canvas to ensure that the fill color fills in the outline without having transparent pixels between the outline and the fill color, and All Layers is enabled because the white background layer helps how the fill can fills in
So i need to change my methods if i want to use a thinner brush, but i'm not sure how i can do this