That seems like a dangerous way to get to be trained. She didn't indicate if he was a dominate or not, his experience level, etc. And, as a sub, imho, you NEVER provoke a dominate into punishment. After all punishment isn't supposed to be fun for anyone so why provoke it? Especially if the person has only talked about training but has yet to actually act on the words.
Plus, she never mentioned what type of training past slave training. Which for her could be something different then for me, then for subbie A, depending on what the understanding and desire is.
And, if he doesn't have experience, which may be the case, to train her then he certainly doesn't have experience to punish her and could do serious harm, especially if he was angered in her provoking him and he reacts during that anger.
I'm sorry but the suggestion in my mind holds no merit except to cause harm (not in a good way) to the sub, which SHOULD NEVER be a dominates first option. And anyone who uses that as a "training method" in anything other then play I would consider dangerous and perhaps even a player and not someone truly interested in the growth and safety of the sub.
Honestly hybrid, without more information it is hard to offer much advice. From the small bit you have stated, if he is just discussing it and not acting on it I am guessing (and it is only a guess) that he is:
1. Not really interested
2. Unsure of what to do or how to start
3. Is interested but not enough to actually put motion to it, meaning he lacks little self motivation in this area.
If #2 is the case that can be solved by a long discussion and several good books and sites about training and for him to sign up for a site like this, look through the threads, and speak to experienced Doms like Ozme, Sir Russell or ID. Basically going through some Dom training so to speak. Or depending on your location you both could join a local BDSM group and attend different items they may offer to help in the training process.
If the reason is #1 or #3 the chances of you getting him to "just do it" is probably relatively slim for an assortment of reasons. And honestly, if the reasons are #1 or #3 what type of dominate would he really be? Would he truly fulfill your needs on a part time basis? (Because, based on human nature, I seriously doubt it would be more then "part time" at best.) If yes, then that may work for you. But, would he also continue with it or would it be only when it works for him? Once again if that meets your needs great, but don't expect him to start training you and become super Dom and stick with it, etc. As many on here could tell you that seldom happens without a lot more bumps and set backs along the way.
All of that being said, sit down and talk to him about it. Explain your feelings, offer suggestions on how to begin, resources of information, perhaps a fantasy or two, maybe something as simple as kneeling by him at times or meeting him at the door that way and put the ball in his court. If it continues to roll across the floor without being tossed at the hoop that should indicate to you his interest and intent.