I don't normally include fractionation in my mp3s. I think this technique works best with live and subjects and experienced subjects. And I write my scripts with the assumption that many of the listeners will be newbies.
However in Subconscious Triggers (a script I haven't yet recorded) I do it once. About 3/4 into the script, I wake the subject, then trigger a light (partial?) trance before saying the fun trigger phrase. I do this because I think a light trance is necessary for triggers to function without extensive conditioning.
Fractionation has several uses.
One use is that it's a relatively easy way to provide a 'convincer', something that helps the subject be convinced that they are entering trance. If you're dropped into a light trance then you come back out, in that moment you can feel the difference between being in and out of trance, so since it feels different then obviously it's working, right?
That's the easiest way to use it like this.
Another is that it's a fairly reliable way to create a greater level of depth in receptive subjects, because you do in fact have an easier time going deeper if you've been hypnotized before, and this is especially true after having just some up from a trance state.
A third use is basically an issue of variance and susceptibility. Basically not every induction approach works as well for every subject. Using fractionation may work well for me, but maybe not for you. There's an argument here that it's not an induction type itself, but an element of another kind of induction.
I would go with mesmer7, I love fractionation, but it is more effective for those experienced with trance. If you haven't gone under before it will take longer to achieve trance, the more you go under the more easily you can be entranced in th future, usually fractionation files involve quick inductions, meaning you might not have enough time to go under and those make it so your just playing along.
Once you gotten good at going under it is very fun going deep then waking up just to end up back down a few seconds later. Usually when you look at hypnotist sites where the have their files available, you'll notice must put out a bunch of basic hypnosis files before they have a fractionation file.
Fractionation is part and parcel of almost every hypnosis show, so it's something that I do, a lot, when performing. In a private session, one can run into an issue when doing it too rapidly where the hypnotee can become disoriented, so one has to remain aware of the hypnotee's non-verbal signals and be sure that they stay comfortable and enjoy the session.
Fractionation, as noted by others, above, is a great deepening technique and is also a good way to cement a trance reinduction trigger as well as as a convincer for hypnotees who emerge from trance initially and claim that "nothing happened." Additionally, in a consenting scene where there is an element of dominance, fractionation can be a really fun way to demonstrate "control" to the submissive by using their trance trigger to drop them into trance while they are in the middle of saying something, while hugging them, etc. (all with prior informed consent, of course!).