This is Paise [sp ?] 164. Here's some tips on creating fine lines. First and foremost, a fine tip. Fine outline tips, that are compatible with cans, that are more pressure sensitive. Pressure sensitive cans allow you to just lightly press the tip. And with that, and a combination of a good flick of the wrist, you'll be able to do a real clean, sharp line. Pre-see your line, pre-place your wrist, pre-feel your way through the line, lightly hit the line, and it's as quick as that.
If you're doing shorter lines, even more so that those pressure sensitive lines are going to work for you. If you find yourself with a piece that you're backed into a corner, you can also cut back into the outline with a fill-in, or inner outline, to make the line appear even thinner. Take your time, lightly hit the tip, wrist action, you'll work your way through it. Keep in mind what you're using, what tips you actually got on your can. Don't forget if you had a fat cap and try to pull off a line like that, you're probably going to destroy the area of the piece you're working on, with drips and whatnot.