Having been in the professional audio manufacturing business in the past, I can safely tell you that only the mechanical portion of the faders should be lubricated with pure silicone. The conductive carbon or plastic and associated wipers should NOT be lubricated. They should be cleaned with a pure solvent such as 91% Isopropyl alcohol, NOT RUBBING ALCOHOL! Don't even think about using any other aggressive solvents like acetone. That will just melt all the plastic! Maybe you should try some gasoline and then have a cigarette?

Sure, there are many kinds of aerosol magic sprays such as the "Caig" brand of magical aerosol sprays that claim to do a whole bunch of stuff but are really inappropriate for volume controls. They are much better for switch contacts, which you don't usually find in faders (except for backstab cueing and automation switches). And for heaven's sake don't use any of the Radio Shaft aerosol "tuner" spray cleaners! Don't even use WD-40.

What I really recommend is, removing your volume controls and immersing them in an ultrasonic cleaner! After a few minutes, pull them out and work them good, put them back in for a few more minutes and then take them out and rinse them thoroughly. Lather rinse and repeat. You'll have beautiful hair and volume controls!

I wash all of my consoles in ultrasonic cleaners! Really!

I'm really not kidding about that! Just ask guys like John Klet, who also restores consoles.

I'm going to wash that Neve right out of my hair.
Ms. Remy Ann David

I had a Ramsa 20-channel board many years ago and really liked it. It sounded way better than the Tascam or even the MCI 400 series I'd had before that. The board had conductive plastic faders, and I used Caig spray with very good results. Remy is correct that there is stuff they make that is better for metal contacts (Deoxit Gold, for example) on switches and jacks. But their Deoxit line also includes Faderlube and Fadergrease, and I've used the Faderlube with very good results on my A&H's that I have now. Go to the CAIG website and do a little research.
Caig is the only company I know of that specifically targets the A/V market (I'll probably get shot down for saying that!). And DO stay away from WD-40! It's only good on pedal steels and kick drum pedals!