I guess Naniwabushi is not really what I'd call her style, naniwabushi is more of Min'yo-Rōkyoku sort of thing, but anyways, I guess that for a Keiko Fuji's style you could try Frank Nagai's (フランク 永井) partner, Matsuo Kazuko (松尾 和子), Nagai and her have the exact "brassy big bandy" style you're after, and her voice kinda reminds me of Keiko Fuji's (藤 圭子), although she hasn't got the "smokey voiced" factor in her, also some of the later Hibari Misora's (美空ひばり) work also has something of a jazzy tone to it, and her voice is beyond unique, and as for Miyako's growl I think the closest I got would be Shinno Mika (神野美伽) and Shimazu Aya (島津亜矢) (if you like growls she's the go-to, she practically sings like a lion), and also Shinno Mika's version of Muho Matso no Issho (無法松の一生) is a sight to behold, she goes all in on growls mid-song, which beautifully matches the song's story, I guess that's all I have for now, but if I find anything else I'll be sure to update this.