Assuming you also want to fuck her front pussy as well, you'll require a cock no more than 60 cubic inches in size, a libido of at least 50 and to have either read the roehm Codex entry or fucked her back pussy before. Once you meet those conditions, you can fuck her front pussy like normal, then continue with her back pussy.
You can also fuck her back pussy by itself, if you pick a cock that's >60 cubic inches (but still under her max capacity of 1,296), but you won't have the option to continue with her front pussy even if you have another cock that's <60, so that's a sub-optimal choice for breeding.
Actually, you need to do both; otherwise, that's potentially up to four wombs going to waste by not being filled with babies. I thought a dedicated breeder like yourself would understand that more than anyone else.
Also, I think she only becomes unavailable for a day (I might be wrong, though; I've never actually played that content). Regardless, I'd recommend staggering the impregnations in such a manner that by the time Steele gives birth, Quaelle's recovered enough to have sex again. Also note that she's no longer fertile beyond 304 days (I think) after she's revealed that she's fertile (and sex has been unlocked), so plan accordingly.
Nope. You can only impregnate the womb attached to the pussy you fucked; as such, fucking both is necessary to impregnate both. Having high cum quality and/or quantity will increase the chance of impregnating either womb, though only to a certain point.
oh, ok, but it doesn’t give you the option to fuck both of her pussies