There are different models of ALPS faders, but I've restored the lovely 'glass-like glide' to several by dismantling the fader (being VERY careful not to 'snag' the wiper tines) and using Mother's chrome polish or -if you can find it- "Simichrome" by Happich (German... and most excellent!) or 'Autosol' chrome polish works well also.
A tiny dab on a paper towel... rubbed into the metal slide rail(s) and then -usually once the polish has discolored to a dark grey- a CLEAN piece of towel to thoroughly polish off the residue.... followed by one more (for obsession/superstition) polish with a clean piece.
Sometimes it's unwise to completely remove the rod from the slider which carries the wiper assembly The P&G faders in SSL's had a sprung friction collar which was VERY fiddly to re-fit if you ever slid the slide rail out completely), so the method in these circumstances is to slip the slider to one end and clean the other, then swap ends and do the rest.
Once the rail is polished (which removes all surface pitting/corrosion/tarnish as well as any airborne contaminants which have settled, and leaves a fantastically smooth finish) he final thing is to add a dab of silicone lubricant. Penny & Giles sells it for maybe ten bucks per tiny bottle (less than a fluid ounce) but it's the EXACT same stuff as "Hellerine", which costs less for more. -Only problem is Hellermann products are not that common in the US, so this is easier to source in Europe. (-They get ALL the good stuff!)
one tiny drop on each side of the rail is all it takes. -Then slide the wiper assembly from one end to the other to distribute the lubricant and push all the excess toward the two ends, and dry the two ends with a clean piece of towel.
While the fader is out, you may clean the wiper contact tines, using a LINT-FREE material. -the best thing I can think of is the 'artificial chamois'-tipped tools for cleaning video heads. A little alcohol and a quick wipe -in the direction which doesn't bend the tines "against the grain", so to speak- is all it takes to do that.
Wipe the surface of the fader track with something DRY and lint-free, a clean, dry coffee filter actually works well for this- to remove any dust and/or debris from the conductive track surface, then gently blow the wiper dry, and reassemble, paying attention to not 'catch' or bend the wiper tines.
You should now experience good-as-new sliding happy-joy-fun-time.
On some P&G faders, the nylon/delrin/whatever collars wear too much, and they don't clean up easily, but that's fairly rare. In my experience ALPS faders with moderate use usually clean up mechanically just fine.