I agree with what has been suggested already. The only thing I can add is that it was helpful to (in non-triggered times) just sit at my computer and ask parts what they wanted to say about a particular situation. Then let them one at a times, say what they had to say. This was safe enough that the blocking parts started to sometimes chime in, which helped me to see their purpose. And then knowing their purpose helped me to understand and accept them, and that helped them to speak up more etc. Understanding some of their role also helped me to identify why things triggered me, and helped other parts do some of the protecting that I needed.

How long? For me, 3 ish years of DID treatment (I had other treatment before) to identify. 6ish years for them to cooperate with treatment, 7 years for their protection to be more gentle with their protection. And counting...