Mike, there is no problem with typical "brass" bore brushes to my knowledge, and I have sure used them a lot in old twist/damascus barrels. As mentioned, even Bismuth shot is OK in these old barrels.
Regarding lubed Wonder Wads for 14 ga.: just use the 12 ga. wads. They are quite flexible and your 14 ga. won't know the difference. I get good 1/4" felt wads, "nitro" OP wads, and OS cards from Mikes Wads. Reasonable prices and he makes all sizes of wads.
Aloha, Ka'imiloa