Use Deoxit - Faderlube. It cleans and lubricates at the same time. (They have multiple products. So choose the one with lubrication. called faderlube or the F-Series).
Mere contact cleaners simply clean the contact, but the sliding surface will become rough and loose contact will worsen in no time. While rotating or sliding, you will feel the contact has become dry /loose / rough with regular cleaner.
Whereas Fadelube will restore the smooth feel and contact conductivity at the sliding surface. And the control becomes smooth but firmer, as it is supposed to be.
Writing this from own experience. It stays for years - I have boxes that were cleaned 10 years before and still works.
If the contacts are physically worn out or damaged no contact cleaner can help, but in normal cases the Faderlube restores it for good time.
It is comparatively expensive, but worth the money. I have bought it online from caig.com . They ship it from USA direct.