The point of cassette bearings, like Phil Wood and King, are that you don't clean and relube the bearings. The seals on the bearings are there to keep contaminants out. Opening the seals just lets the crap in and reduces the life of the bearings inside. When the bearing starts to fail, you replace the entire cartridge.

Compare that to regular cone and cup bearings. Those you have to constantly maintain since a pitted cone or pitted race can mean a minor problem or a complete disaster...depending on which part is pitted.