For all but the tiniest object, I prefer to use a traditional "dip" or "stylus" pen for the ink layer. They're easy to get hold of, inexpensive, and the nibs, being removable are easy to clean (the ink contains a shellac binder which tends to clog if allowed to dry).
I have a bit of a thing for nice pens, pencils and paper, so thought I would share this little website with you. It does everthing that you could ask of a website - tells me about the products, what they are for, how they are used and where I can get hold of them.
A well thought out, simple and informative web site. I've just bought some of their nibs, so I will try to do a sequence of photos demonstrating how I use them the next chance I have.
Update: The DP6H nib is winning for inventory marking at the moment. I'm also finding that Methanol is a good solvent for the ink at the end of the session, and it's not quite so unpleasant to handle as the acetone either....