I can't really picture a
female condom being used for covered ORAL sex. They are also called
receptive condoms. (I've never heard it called a vaginal condom.)
If you want to do covered oral sex on a vagina or anus, you want to use a
dental dam:
http://www.sexualityandu.ca/stis-stds/how_do_i_protect_myself_from_stis_stds/dental_dam
It's a piece of latex you can put over the vagina or anus. Don't pull on it and stretch it out - just lay it on top, a little lube on it helps too.
If you don't have one you can make one from a condom or latex glove. Dental dams and home made dental dams are also great for rimming. They aren't all purple, they can be other colours too, that's just what I found on google image search!
DON'T STRETCH IT OUT LIKE THIS or you won't be able to feel anything. Just drape it onto the bits!
Make your own, just carefully cut the tip off a condom and then slit up the side and roll it open into a square.