I think you have to try to identify the leaders within those communities and let them take the lead.
I'll come back to the context of Haiti. One of the reasons the Brazilians were so successful in rebuilding Haiti, until the disastrous earthquake, of course, in 2010, was that they worked with the local community and sought out the people who were self-identified as the leaders within that community. I think you have to start there.
Again, I don't claim any expertise as a social worker. I know from one of my colleagues and social workers working with the Vietnamese community here that this is very much the way in which they proceed.