Actually, never grease but definitely oil (grease make it sticky so it won't rotate as freely). However, the exact oiling process is not to put some drops in it but to dilute a certain amount of oil and alcohol then dip the bearing in that solution then let it evaporate, leaving a thin layer of oil for best result.
This is correct.
Silencing the rotor properly AND having it last long term requires proper work, and is a lot more than just removing the caseback and putting few drops of oil into the rotor bearing assembly.
The bearings needs to be removed and cleaned with alcohol, and then, like you said, treated with an oil/alcohol mixture, letting it settle properly and then reinstalling the bearings.
Dropping a few drops of oil WILL silence the rotor, but it will in the long run cause issues if the bearings are not first cleaned properly. An analogy (though not the same) is draining the engine oil before adding new one.