As it happens, Dave Moulton just recounted going back to a Brooks saddle in
his blog. http://davesbikeblog.blogspot.com/
He had wanted to use neatsfoot oil to soften it, but couldn't locate any, so used mink oil instead. Someone commented that Tandy Leather sells neatsfoot oil. I also found a whole lot of other products on their site for cleaning and treating leather.
http://www.tandyleatherfactory.com/
John Betmanis
Woodstock, Ontario
Canada