I don't know either, but I will say that for modules that enable H-AI controls during sex scenes the AI not only changes animations often but holds each scene for a very long time, making hentai scenes take stupidly long but it seems to grant results. Of course you can do it yourself.
From what I remember in the editor for the sexual preferences buttons, the buttons correspond to sex acts before and after ejaculation. Conveniently, the major categories are sexual caressing, cockplay, vaginal, and anal for not ejaculating and ejaculating respectively. So I run through them all, and if I built the NPC myself I'm more aware of the specifics of what it likes. Note that bukakke means pulling out and spraying, while cream pies is staying inside so along with button select you need to remember to put it out or in.
I think number of pose selections in the things the NPC likes is important, so know its preferences then do a selections of what it likes. Ejaculations don't necessarily satisfy preferences since some button preferences don't align with ejaculation.