The electronic logic deadbands have been designed wide enough to cater for nominal resistance variation due to wire lengths, contact wears, signal noise etc.
For those often use connectors, contact cleaner would be sufficient.
You do not apply any grease onto those tiny contacts, as it will exacerbate the problems even worse. This is not an automobile lead acid accumulator.
In real life, if the spring force of the contact has lost its effectiveness, the only solution is to change the connector as no amongst of cleaning will resolve the connection problem.
No, you do not scrub those tiny connectors, those are tinned, if its already corroded due to acidic spill, the only real solution is to change the connector.
If you need a better advise, you will need to be more specifics and upfront with your problems.