Filling linework with color?

I do comic-style art with very thick bold lines. When I color, I simply block in a space with solid color, and use masks and filters to shade or blend. Right now, the only way I can color in an empty space is to do it by hand with a brush tool by making another layer underneath the linework, and carefully line the edges so it's a solid block of color. The paint bucket tool will leave a small area around the linework of empty space, otherwise I would use it instead. Below are examples of what I'm talking about.

Colored by hand using the brush tool (color layer is underneath the linework layer):

Colored using the paint bucket tool (all one layer):

If I could use the paint bucket tool or something similar to just drop colors in wherever I need them instead of having to hand-paint it all in, it would cut my drawing time in half.

Anyone have some suggestions? Thanks in advance.