I would like to create a segmented look of my spaceship with hatches and paneled armor segments. I have the outline of it already modeled, but I am lost how to create the segments. I don't want to model them, I would much rather paint them on with a texture.

UV unwrapping gives me a texture, but painting the UV externally makes it very difficult to figure out what the final distortion will be.

How can I paint on nice, straight geometric lines directly onto the model?