I put a thick, heavy, goopy coat on the underside of my various Brooks saddles. The unfinished leather soaked it up within a day.
I put 3 or 4 light coats on the top (finished) side of the saddle over the course of about a month or two. That allowed time to soak in. Used the polishing cloth to get the excess off before each ride during that couple of months.
Now that my saddles are generally matured and broken in, I only put proof-hide on every 3-6 months. A thin light coat that I let soak in and wipe off before my next ride.
"If Americans want to live the American Dream, they should go to Denmark." - Richard Wilkinson