Hi
You have to take them apart, I have used alcohol then trombone oil on the rails and fader lubee on the tracks (CRC?)
just a tiny bit. I also found you only get like 1 cleaning disassembly before they are break but it does help sometimes
However I found its better to just replace them (cheaper then you think) as they are usely worn out in a few spots. I been changing 12 a year (center section) so i always have nice faders for the vcas
and in a few years you end up with all faders
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