I don't read much ero manga with feet because I feel like they are often not drawn super consistently or stuff gets into weird foot worship and smell territory which I am usually not thrilled with. I generally just stick to pixiv and booru illustrations for my anime girl feet.
Hentai manga by Saito Yamashiro No Kami Yukihiko has some nice shots. He's got a few chapters posted on Fakku and I first encountered his pixiv stuff before that. Some of his non-foot anatomy is wonky, especially penises, but fuck it, ya'know? I also bought Renai Sample by Homunculus recently because while it is not really focused on foot stuff at least the dude can draw them. XD
I'd say check out the danbooru
Perfect Feet image pool and see if you like some of the artists. It is no anime foot Mecca, but it's a very good starting point with most of the good illustrators represented.
I'm also totally useless when it comes to the nail polish thing. I don't like polish either IRL or on my anime girls. Natural toes is best toes. Also I miss the appeal of high heels and stuff... Oh well, to each his or her own! Hopefully I was somewhat helpful even if I sort of skirted around the edges of your request.