I honestly don't think you have to deactivate them to deprime them. If the bullet and powder haven't been removed, do that first and then just deprime as usual. With the primers upside down, there is nothing for the anvil to press against so the probability of them going off is nil.
If you do feel strongly that you need to deactivate them, I sure wouldn't use oil or anything like that. First of all, it may not deactivate them and secondly I wouldn't want to have an oily case to deal with.
In any case, you do wear safety glasses at all times while reloading - right?
