If I can speak honestly about this…
When I first applied to airlines, I considered doing a "training day" to prepare me for the interview, and read over the syllabus of the different day or two day courses that were being offered for £100-150 etc… I thought about it and eventually decided that I could not spare the money as I was struggling financially at the time.
After my interview with my current airline (7 years ago…), I was glad I had not paid the money.
The things that were on the syllabus would have made no difference what so ever. They were more interested in my experience of dealing with people.
So, if I am being honest, I really don't see the value in these sorts of training courses for cabin crew.