DS2 (17mo) is going through a bad phase of this just recently. Worse, when he passes out, he doesn't immediately start breathing again, which is very scary.
DS1 was a breath-holder (I assume you mean that they breathe all the way out and then can't take a breath in? That's what DSs both do/did) but he never passed out, thankfully - I used to poke him in the solar plexus to try and get his diaphragm to release so he could breathe in. MIL says DH used to do it too, when he was having a tantrum - but when he passed out and fell to the floor, he would immediately start breathing again.
Non breathing after passing out is something new to her (she's a nurse as well) so DS2 is taking it to new levels of scary. The first time I gently pushed his chest to get it moving again but the next two times, I breathed into his nose.
Blowing into his face doesn't seem to work, unfortunately - if I had water to hand, throwing that at him might but I don't always and he goes out VERY quickly - so I've had to resort to slapping him on the side of his chest (MIL advocated pinching his earlobe, another tactic) to avoid it.
He doesn't always do it in tantrum, last one he did was because he ran his face into the door (forgot to put his hands out to stop himself).
I've seen a consultant paediatrician who thinks that there's nothing much we can do that we're not doing already - DS2 is otherwise healthy - the only thing that might help is having him checked for iron deficiency, as low iron status can contribute to this situation. Other than that, just wait for him to grow out of it and try to avoid him getting into those situations.
The paed did say that he seems to have an overly sensitive autonomic nervous system, but there's really nothing we can do about that!