Dave, I try to replicate a steel color, as well. However, I would neve attempt to do it in situ. I'm just way too clumsy. Instead, I place my monofilament spool on a bamboo scewer "spindle", then pinch the line between a sheet of cardboard on my bench and a broad tip black Sharpie and pull it through. I keep going until I have several feet of it, at least enough for the job at hand. I then roll it all back on the spool and repeat the process using a silver Sharpie. I end up with something resembling steel without the paint build-up and I can still fit two lengths of the stuff in a .33 id brass tube. Your rigging looks awfully good, mate. Why mess with a good thing?
Cheers,
Bud