I think we've done something similar. There is a point of no return in the meltdown process, which can be somewhat unique to each individual. If the situation is not mitigated before you reach that point, it won't be. Over time, you learn the steps leading up to it, and where it is. I think Tracker in the book he is working on has a description of how he views the meltdown process and why you can't stop it at a certain point.
Definitely learn where the point is and all the signs that happen before.
_________________
Mom to an amazing young adult AS son, plus an also amazing non-AS daughter. Most likely part of the "Broader Autism Phenotype" (some traits).