Hi. I guess you've been talking about carbon faders so far. What about plastic conductive faders?
Nope. -Conductive plastic.
You probably don't want to concern yourself about the conductive material if the fader is working correctly.
If you're talking about 'feel' and 'stiffness' then it's almost certainly got nothing to do with it. I don't think I've ever encountered a fader where the friction of the wiper against the conductive material has been responsible for making the fader feel 'stiff'.
Instead, the slide-rails (usually a polished nickel or chrome) and any bushings which slide along them (they may be nylon or some soft bearing metal) are the only things which need to be addressed.
Clean. Polish. Lubricate.
Assuming that the bushing/s aren't worn to a point where they cause the slider to 'gall' (which I've seen on some Penny & Giles SSL master faders) then that's all you need to do.