Don Wheeler
The PITT pens are neat if they have the color you want. The advantage of the old dip style pen is that you can use any modeling paint if you thin it enough. Cleaning is pretty easy; just dip it in thinner and wipe it off.
One reason I posted this is to point out that there are alternatives to trying to do ridiculously fine lines with an airbrush. Even airbrush artists will sometimes use pencils, brushes, or even scratching to do fine details.
Don
My problem with the PITT pens is the price. For highlighting and details, I think that they have every color that I may need.
Black, Cadmium yellow, Indianthrene blue, Phthalo blue, Pink carmine,
Cold grey III, Cold grey IV, Caput mortum, Leaf green, Orange glaze,
Middle purple pink, Purple violet, Dark phthalo green, Magenta, Warm
grey III, Raw umber, Sky blue, Ivory, Light yellow glaze, Scarlet red,
Light cobalt turquoise, Cobalt green, Light phthalo green, Light flesh
They have metallic colors too which are even more expensive. I have not used the PITT, just quoting Gerald for other users.