First I would use a reliable contact cleaner – here are a few I use and recommend.

• DeoxIT-D5 by Caig Laboratories, part number D5S-6. It improves conductivity, deoxidizes, seal & protects connectors and contacts.
• Cramolin-R-5 by Caig Laboratories, part number Cramolin R5. It cleans, preserves and lubricates contacts on moving and stationary parts.
• Spra-Kleen by GC Electronics, part number 8666. It’s a good electrical contact cleaner and lubricant.

It is important to keep the same potentiometers in vintage instruments. If a volume control is worn, try using the tone control as a replacement and put the exchanged volume control where the tone was. The tone controls should last a good amount of time because they don’t get used as much as the volume.