I was experimenting with polishing tilt mech bits during my work on the Tilt film.
I found that it is difficult to polish lead. And also, that lead is resistant to corrosion and might never need to be polished in order to have better conductivity.
So, with exception of lead plumbs, go ahead.
Also, find a way to have firm metal-to-metal contact all the way from the plumb to the wire.