Will scuffing a polished ball cause more oil to be extracted during the de-oiling process or will leaving it polished allow the same amount to be extracted? VIVALD
If you don't to dull the ball down for any other reason, I wouldn't bother to do it for any de-oiling procedure. If you do need/want to do it, then do it before de-oiling.
I have seen no proven reason for dulling a ball to enable more oil to be extracted. Dulling only affects the surface Ra (hills and valleys); oil is not at the surface and you're not making the pores in the resin coverstock any larger by sanding it.