I re-started my cycling a couple of years ago with a town bike fitted with a Brooks B33, and I rode it everywhere without funny trousers, no problem. When I bought my Boardman Road Race late last year, I found the standard Boardman saddle to be absolutely agonising after about 15 miles, even with padded trousers. I bought a Charge Spoon off
ebay and tried that; a bit better, but not much, so I bought a gel padded Selle San Remo. This was quite a lot better, and I started to be able to do 20+ miles without too much trouble.
Today, just as an experiment, I refitted the original Boardman saddle and went for a tootle round the lanes. I racked up 26 miles with no discomfort at all! This might mean that if I'd just applied rule #5 I might have been alright without changing saddles. I'm more inclined to think that using the San Remo as a half way house to help toughen me up has done the trick without going through the purgatory I would have suffered without changing saddles.
To sum up, my experience suggests to me that, given time and miles under the wheels, we can modify our rears to suit our saddles, but it's a hard process, especially when like me, the rider is not in the first flush of youth.