I was looking it up the other day to find out more about it and some of the strategies are things we use on our own or in t anyway. From what I read there were tons of grounding strategies and mindfulness exercises involved, and we find those really helpful. One webpage we found had a whole lot of grounding / mindfulness exercises to use on the site, which was cool.
EMDR strategies are good for us too.
I think mostly DBT therapy is used for BPD (borderline PD) but it seems like there are heaps of useful things in it. It might be worth a go.

ETA: its helpfulness with DID would simply be that the grounding and mindfulness strategies help with keeping the nervous system on an even keel, which can be helpful for any trauma response. It's just about moderating emotions and the nervous system (self calming when triggered etc)