The best way of course would be to dig in to see how bad the faders are. Sometimes there are significant contaminants (dust, dirt, cigarette smoke residue, drink spills, etc.) on fader surfaces.
If this is not your first choice, you can try using the two DeoxIT® Fader sprays, F5S-H6 and F100S-L2.
If you have significant contaminants (listed above), we recommend using the F5S-H6 first. This has a solvent to help displace the contaminants away from the contact areas, as well as applying the DeoxIT® Fader product on the surfaces. Just spray a few short bursts into the fader. Depending on access, you may require the 45-degree attachment (PS-SS45T). Then apply the F100S-L2. This spray has no solvents and will provide more lubrication or and protection.
If you require more tactile feel to the faders, we then recommend the DeoxIT® FaderGrease.