I believe my lover & I must avoid contacting any part of me that's been in/against her anally into her vulva/vagina, without appropriately cleaning me first. But we've no idea: 1) what's an ideal cleaner, 2) what time-duration makes it unnecessary (since we are regularly apart for several days, our playtime's start @ a couple hours). I doubt we've a unique, or even rare concern here, so if you've a link that answers our questions, that"s great as well.
Thanks very much!
It sounds like you've done your research when it comes to switching gears from back to front-door loving. Those lady bits can be extremely sensitive when it comes to new bacteria, and even a millisecond of ass to vag - whether it's a finger, a mouth, a toy, or a homegrown cock - may result in an instant yeast infection for some women. So yes, it is never recommended to go from ass to vag unless you've taken proper precautions to clean said toy/body part.
To answer your first question, I would say your average household body soap/shower gel should be sufficient. If she knows she is susceptible to yeast infections, a glycerin-free soap may be preferable as glycerin can also cause yeast infections for some women. Make sure to wash all the soap off, and lightly scrub around any crevices where bacteria may hide (i.e. head of penis, foreskin, fingernails, etc). If you are dealing with toys, most non-motorized, non-porous sex toys (such as silicone, glass, or stainless steel) can be boiled for a few minutes, or even thrown in the dishwasher for a thorough cleaning.
In reference to your second question, I really don't know if you have a window for when the post-ass play bacteria is no longer an issue for said vagina. I'm sure some of the bacteria will die overtime, but nothing is certain, so your best bet is to clean the area before diving into V town.
Is all this shattering your dreams of spontaneity? Or perhaps you're a huge fan of double-dipping, and are in need of an ass-to-vag- friendly option. Well, have no fear, because condoms are here! Yes, not only do condoms protect against pregnancy and those pesky STIs, but they also allow for a quick and easy cleaning solution for all of your double-dipping needs. Here's the rule: for anything that goes in or near the anus, use a condom, finger cot, or dental dam. Once it's time to move to V town, all you have to do is carefully dispose of this latex/polyurethane/polyisoprene barrier, and viola!, you have a clean working space! Yay!
And that's not all: Using toys? Well you're in luck, because condoms on sex toys are every double-dipper's dream come true! Dildos generally do not change in size/girth (such as that of a homegrown cock), so you can layer multiple condoms on your sex toys, removing one every time you go from ass to vag. Oh, the possibilities! ;)
For more info on anything anal, checkout "The Ultimate Guide to Anal Sex" (there are two versions, one for men and one for women). Hope this helps!