There has been lots written about this. I suggest you make good use of the forum search function (top right of each page) first before you ask people to retype information already easily accessed.
I used Brooks saddles for years on my mtb's along with others in our gang in the Rockies on hard tails. Mostly Pro's and B17's. Everyone soaked theirs in a bucket of warm water before immediately using for a nice long ride and then only treated with Proofhide after.
I now live in the OR and use WTB saddles due to the wetter overall climate. I still have a nice sprung Flyer hanging around that I ended up with so if that is the model you are after shoot me a message!
Stock photo but pretty close in color, mine is a little darker from age but never got the soak treatment and little use.
I just picked up a slotted c19 (rubber). I've only ridden it once and the seat wasn't adjusted properly (too far forward). I'll report back once I'm able to share a real opinion on it.