For as simple (usually) as it is to slide the sights out, I think it would be advantageous to brown all of it and then reinsert the sights. It would help to keep those crannies from rusting later, I believe. Put successive coats on until you are happy with the appearance. The more coats, the darker it gets. I probably overdid it with mine and it looks almost blued. I like the appearance and nobody else has to like it.