No easy, sure fire way I'm afraid. I have used a draftsman's .005 pen and that works pretty good. You can find them at art supply shops. You could go the rout of free hand with a fine brush and take your time with black paint. I've only seen two or three really pull it off right tho.
I have tried using black decals to make them before, but it is very hard to get them to conform to the surface and stick correctly. If you come up with something let us know.
Oh, and welcome to the forums Come back and post often