In response to the 'effortlessly' remark, I'm sure no conditioning can be done effortlessy. I can tell you it happens unintentionally, though, which might make it seem less of an effort.

In retrospect I think it was the combination of two training-exercises that did the trick: firsty a daily round of self-stimulation without being allowed to climax to build her self-control and secondly, if you do allow her to, always dragging it out, making sure she only waits for your permission and nothing else (and knows it).

Plus, never allow cumming without permission, the training never really ends. This 'skill' is easily lost, it has to be maintained. I'm betting the most important aspect (as always) is the mental one, so other training might work just as well as long as she knows who is in control of her orgasms.

I hope this helps. Do tell us how it worked out.