Unless you are changing to a different lube I see no reason for cleaning it out. Bullet lube doesn't die from old age and the machines aren't made to allow removing it readily.
The only time I ever "cleaned" my Lyman 450 was to switch from the original Lyman black lube to the NRA formula Alox. I simply removed all the parts and put it into a bucket of water. Heated the water over a Coleman stove until it was boiling and the lube melted out, floated to the top. Inside it was a clean as if new. That was in '71 and it's never been cleaned (internally) or had the lube replaced since.