Once I've pulled the axle out, I hold the wheel upright, with the hub horizontal (as it is while riding).

Then, I add a dozen drops of motor oil into the open end of the freehub body, just behind the dust shield (which I never remove).

After 30 seconds or so, I tilt the wheel/hub slowly to the left, so that the oil slowly creeps in behind the bearing cup in the freehub body.

Unless the hub has previously been over-greased, the oil runs right in, and there's no dirt there for the oil to wash into the bearings.

Then I spin the body, and turn the wheel to different positions to distribute the oil.

It helps to heat up the freehub body with a hair drier before adding the oil, it will penetrate faster, but is usually not necessary unless the temperature is low or the oil is a thicker grade.

I also have an oil squeeze bottle with oil that has been diluted with solvent, and this stuff penetrates fast without the benefit of any warming.

Count me in as one who hasn't felt the need to ever take a Shimano freehub apart.