It's only very recently that I purchased a fine chalk line for precise work, it came preloaded with blue chalk and that's what I already have on hand for my older lines.

I find snapping precise lines over 8' or so is a challenge when working solo so I stretch a masons cord down my timber and pick useful pairs of points along the cord. My lines are then inked on with a fine point rollerball pen (usually black) and straight edge only in the areas I need them.