Also, and sorry if I missed it, but a nice quality short/bibshort is a must. When I started riding road a couple of years ago, I thought I would never get over the sore butt.
Now I can ride most modern saddles, and even some classics like Brooks or Avocet with no pain.

Another thing that I never thought of is posture. I used to arch my back like the hunchback of Notre Dame. After I realized and corrected the problem, I now have reduced the focused pressure on my butt even more. I can and have done centuries with little problems.