I've ridden a Brooks B-17 Narrow extensively since 2007 both with running shorts over completely unpadded sports underlayer, and with CW-X triathlon shorts that have limited chamois. For four years prior to that, I was riding stock saddle (and am lucky still to have my reproductive organs, we can be sure).
I wore the running shorts/unpadded underlayer (the combination being even less thick than basketball shorts) when the saddle was new and that was far and immediately superior in feel and endurance to wearing standard cycling shorts on a stock saddle. I purchased the CW-X's BECAUSE they have limited chamois while offering other characteristics that I enjoy, not because I found padding to be necessary on the B-17, even in its narrow form.
More important than break-in I found is getting the perfect seat-angle with a Brooks. I now have mine just ever so slightly rearward. Using a carpenter's level helps.
I love, love, love Brooks, but Selle Anatomica is also worth checking out, one has to admit. Best of luck.