First thing I said as I saw your picture, ooh that's nice was the sky burnt in or is it natural? Before you ask, I am pretty new to this game (last 3 months in Black and White) so any advice passed on is always valuable.
Sky is natural.... use of a red, #25 filter will seriously darken a blue sky with traditional B&W film..... it will do nothing for a "silver" sky..... a #29 will do even better..... & tanks for the kind words....