Plenty of ways to skin a a cat. I have made a bunch of bench made sights with several different types of faces, gold, ivory and silver solder. If you want a brass face then I would using a small drop of brazing rod. I usually rough mill the steel portion of the sight, then solder or braze on a blob of material, then continue shaping until complete. A nice job of brazing will stay put forever. If you silver solder or braze the face on you can blue it without a worry, I usually finish the front sight inserts in nitre salts. I use G-flex epoxy and drill a small hole to set the ivory inserts in. Good luck!