I think there is a serious gap on the Brooks site regarding the lack of information on correct saddle selection.
Rivet have a guide for measuring sit bone widths and then choosing a saddle for your intended riding position.
Which Saddle is best for me? is highly recommended reading.
When the saddle is initially moulded (which Rudi and I both do), it is done by soaking the rock hard flat leather piece in water so the vegetable tanned leather becomes malleable. Then it is formed into the desired shape by appling pressure and allowed to fully dry.
Wet leather AND then
riding it for a long period when it is wet will cause the leather to stretch. That should be avoided. It is the same process that is used to shape the leather, but it is uncontrolled!
However with normal riding the leather will form to your body shape (ie sit bones) by the bodies normal perspiration/humidity and the pressure points localising the stretching of the leather. When the leather has stretched at the localised level and equalised the pressure, it is then formed to your body shape, something a hard plastic saddle can't ever do.
Rudi has very well detailed how this 'breaking-in' can be accelerated in a controlled manner but without the excessive use of chemicals which will very much shorten the life of the saddle.
If your saddle is within the recommended range for your sit bones and riding style, the damp towel, letting the damp leather 'rest' then a short ride, then let it fully dry to your moulded shape is sound. It uses the properties of the vegetable tanned leather to your advantage.