De-Ox-It is not the best way to clean dirty cap plates...it is a contact cleaner/enhancer designed to improve conductivity between two metal parts. I have successfully cleaned caps in vintage radios with 91% Isopropyl alcohol, blowing it out with compressed air. This is cured several tuning caps that crackled when tuned or even shorted out in places.
i recommend 91% Isopropyl mainly because it leaves less residue than 70% which may have other additives in addition to water.
I HAVE used De-Ox-It on the contact points in tuning caps, using the pinpoint applicator rather than the usual spray. That has worked well.