Contact cleaner (no residues) + lubricant: Apply contact cleaner and turn the potentiometers (pots). (Dissolvent will be distributed on the resistive track) Test the pots. All scratchy noises should be be gone when the pot is turned. If needed, wait a bit and apply contact cleaner again. Turn the pots. Ideally, let the contact cleaner evaporate before applying lubricant. Turn the pots. (No harm is done applying the lubricant before the cleaner has completely evaporated, but there will be a greater chance that the contact cleaner dissolves the lubricant, which limits the lubricating effect.) Contact cleaner with lubrication: Follow step 1 and 2 only. If the resistive track is totally worn down, cleaning & lubricating might only help as long as the pots are “wet” after applying the products. Here, the pots will typically become scratchy again after a day or two. Replacing the pots are needed. Some products like WD40 will both clean and lubricate, but leave a sticky surface on the resistive track that attracts dust and might harden over time leaving a non-conductive film on the resistive track, which will worsen its performance. However, if a potentiometer is treated with WD40, it can easily be cleaned and substituted with a better lubricant.