charjohncarter
Veteran
That should be enough to clean the contacts, in fact the contacts that you show look good. We can't see the bottom ones but if they look like that they look clean enough. I've used De-ox which is a spray deoxidation cleaner. But what you have tried ought to do the same.
If you have a continuity checker (multi meter) you might put it across the batteries that are showing and see if there is juice.
If you have a continuity checker (multi meter) you might put it across the batteries that are showing and see if there is juice.