That will clean it, although 800 grit is probably a bit more aggressive than you need. It won't stop it from oxidizing again though, that's what dielectric grease is for. In most cases it is not needed but this can be an issue in humid environments.
Dielectric grease is not so popular in my country. We have contact cleaning spray with oil and dry contact cleaning spray. Not sure of difference and whether these sprays can be a decent substitute for dielectric grease...
Also we have WD40 Specialist Contact Cleaner.
And Mr McKenic – Contact Cleaner (Fast Dry) with features:
- Cleans Precision Electronic Parts
- Degreases
- Removes Dirt & Flux
- Improves Electrical Conductivit- Fast Drying
- Safe On Most Surfaces
- CFC Free
Not sure whether it renews conductivity and further protects electronic contacts.