Not sure of the actual intent of some of the procedures described above, but you do not want to flush all the grease out of the freewheel innards and leave it devoid of grease. If the only remaining lubricant is oil, WD40, or anything not including grease, it will not last any length of time. Any liquid lubricant such as oil or WD40 will most assuredly drain out over time, due to gravity and centrifugal force, leaving the innards dry. You don't want that.