Could you first treat with DeOxit from Caig? The Caig webstie reports:
DeoxIT Power Booster is a fast-acting deoxidizing solution that cleans, preserves, lubricates and improves conductivity on all metal connectors and contacts. Use as a general treatment for connectors, contacts and other metal surfaces, and on non-critical metal surfaces with severe oxidation and corrosion. If the metal surface is discolored, it is severe. DeoxIT dissolves the contamination and protects the surface. For reference, DeoxIT has approximately 20% cleaning action.
DeoxIT Power Booster, #DN5S-6N
NEW . . . DeoxIT Power Booster DN5 Spray, 5%, 150 ml, non-flammable, non-drip and safe on plastics!
Part No. DN5S-6N
(NSN 6850-01-519-5548)
DN5S-6N replaces the earlier non-flammable version of DeoxIT Power Booster (which used 141b carrier solvent), with a new environmentally-safe solvent.
Price: $17.95
Caig also has other methods of applying DeOxit, if you don't want to do the spray thing, such as a little squeeze tube for $5.95 + shipping.
After cleaning you could go with the Caig ProGold, or Walker SST (careful applying the Walker - a caveat, I'd check with Walker before applying to a phono cartridge, to see if they approve that use of SST).