One of my clients used an ink-spitter on mylar to produce "films" from which he made his PCB's. Those were not of the sort that you'd be able to touch up with any hand-held device, since the lines were on the order of 5 mils. The odd thing was that the color that seems to have worked best was sort of a chartreuse, or the like (Keep in mind that I'm "chromatically challenged") since exposing the resist requires intense UV, which that color seems to obscure quite well. He's the one who wound up with the old Gerber plotter, however, so he clearly recognized the weakness of using a printer.

He built his own multilayer PCB's in his basement, and did a fairly decent job of it, too. He was, after all, a chemical engineer. He wasn't happy with his LPKF mill, and used it only for drilling. I believe he uses a laser drill now.

AFAIK, none of the Gerber plots ever needed hand-editing, nor would it have been realistic to attempt it when drawn line widths were below 5 mils.

I currently involve myself very little in PCB fab and assembly, preferring to focus on rigorous testing of the bare boards and the completed assembly. I just send the files to a PCB house in other parts of the world and rely on them to make 'em. I just make sure I get what I pay for.

RE