Info from here
"There are many fables as to the best way to soften the saddle. However you do not want to soften the saddle, you want to promote its forming without it becoming soft. A good saddle will still look and feel hard but it will have taken to your shape. Consider your best, hand-made leather dress shoes. The first time you wore them the leather was hard. They pinched and you got blisters. But after a few months they felt better than any shoes you ever owned before. The leather is not any softer, it has formed to your feet so the shoes are now truly custom fitted.PS - +1 on the 'nice picture' front. Lovely warm tones...
This is what a leather saddle can do for you if you treat it properly. And the proper way to break in a Brooks saddle is to ride it. A perfectly broken-in Brooks saddle is still hard at every point, even where indented, as no foreign substances have been used to accelerate its breaking in. The rider's contact with the saddle is now uniform, with no pressure peaks. The saddle may look distorted but to the owner it is incredibly comfortable – exactly how a Brooks should ideally become. How was this form achieved? Simply by riding.
'Proofide' does not accelerate the breaking-in process. It conditions the leather without saturating it, allowing it to breathe whilst offering some protection from the elements. A saddle that has been treated with Hydrophene or Neatsfoot oil may appear comfortable but this comfort comes from its bowing. Brooks' official advice is lots of Proofide on the underside without wiping off – to protect the saddle from anything thrown up by the wheels (not so important on a bike with mudguards). On the top use it sparingly every 500 miles: apply in the evening, wipe off in the morning."