Not soaking in Oil, but absorbing Brooks Proofide .. you apply it underneath the saddle,
body heat absorbs it into the leather ,
I have sped the process up by warming the saddle upside down in a warm oven ,
no more than 100 degrees F.

brooks pro favors a racing posture, B 17 a more upright one.
the back plate is arched on the pro, it's flatter on the 17