I've elsewhere explained this, but it can't find it to link to it.
Here's my writeup which I saved in case the question was again asked.
I. Why Remove Corrosion from Contacts?
Corrosion increases resistance or creates semiconductors with peculiar and non-linear, properties. Sulfides and oxides are semiconductors. Metal oxides were the first diodes, and one may construct a radio using a homemade metal oxide, including a rusty razor blade. Corrosion is consequently not a benign layer, but given that we live in a corrosive environment filled with oxygen and sulfur we must find ways to remove it.
II. Abrasives Can and Will DAMAGE or DESTROY the Metal Plating on Contacts
Plating on electrical connectors is most commonly tin, but is sometimes nickel, silver, gold, or rhodium. Silver, while harder and having lower electrical resistance, forms oxides and sulfides which act as semiconductors and insulators. Gold is softer than silver and readily abrades away, and is a poorer conductor than silver, but it does not readily combine with oxygen or sulfur. It is therefore used to passivate and seal the surface and thereby prevent corrosion.
Any significant abrasive—knife blade, pencil erasers, sandpaper, emory paper, steel wool, abrasive plastic pads (tradename Scotchbrite), wire brush, desoldering braid, etc.—will damage, degrade, or even completely remove the pin's plating, reducing electrical conductivity (increasing resistance) and increasing corrosion over time. The deep scratches will also create a rough surface which will further abrade the interior of the individual receptacles in the tube socket, damaging pins as they are inserted or removed.
So using any abrasive on the thin plating layer will damage or destroy it, creating more problems for the future than it currently solves.
The solution to removing corrosion is safe, simple, and effective:
(1) a cleaner which complexes the corrosion. DeOxIt (see below) is such a cleaner.
(2) very mild metal polish which combines the complexing agent form (1) with a mild abrasive.
III. Ingredients in Metal Cleaners and Metal Polish
Metal cleaners and polish are made from simple and generally safe ingredients:
(1) Optionally a mild Acid (commonly citric, sulfamic, oxalic, etc.) to break up the corrosion—metal oxides, salts, and sulfides—by removing the metal ions and permitting complexing into something soluble which can be washed away. Without an acid of some sort the cleaner will not be able to remove thicker or harder layers of corrosion.
(2) A surfactant (wetting agent), detergent (cleaning agent), or chelating agent (metal complexer) to (a) form a soluble metallic soap with the removed metal ions such that the soap will dissolve in the carrier, and (b) make the polish spreadable across a metal surface by reducing the carrier's surface tension. The stearate is commonly oleic acid (olive oil and the main ingredient in human fat), palmitic acid (palm oil), stearic acid (vegetable oils and animal fat), etc. The common chelator is EDTA which, as a bonus, further acts as a water softener by complexing the calcium and magnesium.
(3) Solvent carrier (water or petroleum, typically deodorized kerosene or naptha), usually with some petroleum solvent or organic solvent like acetone to better dissolve and remove any polymerized (crosslinked) oils and other dirt, including monomer (the building block for polymers)
(4) Optionally, fine abrasive to assist in gently breaking up the hard oxide layer without removing significant material from the surface.
(5) Optionally, an anti-corrosion additive, such as a chelating agent like EDTA, or benzotriazole (BTA), to bind to the metal and prevent future corrosion. The EDTA, again, is also being used as a water softener and chelator for the corrosion, so it serves multiple purposes at no extra cost.
The remaining ingredients tend to be thickeners and pH adjusters.
IV. Ingredients in DeOxIt
DeOxIt is a combination of stearic acids (oleic and palmitic), again to dissolve and solubilize the metal corrosion, in a hydrocarbon carrier. It's non-abrasive and likely relies upon the mechanical force of the contacts moving against each other, potentially plus dissolved material as an abrasive, to help break up the corrosion layer. It doesn't contain a mild acid to remove metal ions.
The fancier DeOxIT Gold adds Difluoroethane to the mix. Chloroflurocarbons are wonderful solvents, which is why industry used them for decades, just letting them evaporate after use and thereby destroying the ozone layer. Difluoroethane is not seriously ozone depleting, well, not as bad as the CFCs it replaced, and photodegrades in a few years, more or less, and is often used as a relatively safe propellant and cleaning solvent, as long as it is not deliberately concentrated and inhaled.
Because DeOxIt doesn't contain an abrasive, it tends to need some mechanical force to assist in removing hardened corrosion from pins. Again, this is normally provided by the friction of the switch contacts making and breaking as the switch is moved.
The solvents carrier is volatile and does not long linger after application.
So the heat from a tube is not going to cause any problems. Any residual stearate left on the contact will simply evaporate from the heat.
The mechanical force to insert the pin is likely high enough that in a tight socket no cleaner remains between the socket and the pin.
V. Purpose of Abrasives
Adding a mild abrasive helps to break up the hard surface of the salts, oxides, and sulfides so they may better complex with the stearate and be removed.
This is why the Nev-R-Dull wadding polish uses a more abrasive cutting agent to faster remove corrosion. It is also why museums won't use it to polish metal objects, as the abrasive removes surface material, not merely the undesired corrosion.
Whenever a metal surface has been roughed up it will have a dull appearance because the light scatters in the fine scratches. Think jewelry, silverware (solid or plated), metal trays, or aluminum car rims. Using a very fine abrasive permits the polishing of plated surfaces to a smooth (bright surface) by smoothing the edges of fine scratches and removing some material to smooth the surface.
VI. Conclusion TL/DR
Cleaners like DeOxIt will remove light corrosion, but this requires physically working the contacts. These cleaners will not polish the surface, i.e. remove fine scratches or smooth the edges, smoothing the transition between switch states.
Corrosion is sometimes thick and hard, and thus difficult to remove. In such circumstance a little abrasive goes a long, long way to making the connector bright and shiny, with excellent electrical properties. Electrical connectors can be cleaned using Mother's Mag and Aluminum Polish or the 3M Mag and Aluminum Polish, or the very similar 3M Chrome and Metal Polish. Blue Magic is similar, but not as effective. I then suggest cleaning with a lightweight solvent, such as the CituSolve (tradename for limonene) which is a terpene derived from citrus rinds, to remove any residue.
My experience has been the three polishes I above listed three work better than the common household polishes like Noxon or Brasso, or the Gorham Silver Polish. All of which I have in my house, BTW. The Noxon and Brasso will generally not deliver the same mirror bright finish that the Mother's Mag, 3M, and Blue Magic can create.
I inherited some silver which had not been polished in decades, and the sulfides and oxides were so hard it was impossible to remove with Gorham, Noxon, or Brasso, at least not without substantial effort. The Mother's and 3M easily removed it and left the surface mirror bright as if brand new. I have similarly polished silver contacts in rotary switches. The resulting contacts were shiny and immeasurably low resistance on my multimeter, unlike when I started.
Edit: Fixed formatting.
