WD40 is fine for removing a boss this way if you spray it from the engine side around the crank and into the keyway slot, straight auto fluid or Kerosene would also work.
Any hammering or slide hammering of the crank up or down is likely to crack the alloy end covers.
The bearing clamp must have the key way lined up so it doesn't get caught in the clamp when removing the boss,see A2 image.
I usually use the grey handled hammer under the boss then hit the other side of the boss with the other hammer but being careful not to collapse one of the 3 bolt holes in the boss.
