We use all of before personal pronouns (us, them), demonstrative pronouns (this, that, these, those) and relative pronouns (whom, which). The personal pronoun is in the object form:
I need to speak to all of you for a few minutes.
He brought gifts for all of us.
We had to contact the insurance firm and the airline, all of which took a lot of time. (all of which = ‘contacting the insurance firm and the airline’)
With demonstratives (this, that, these, those) we can say all of or all without of:
[talking about a pile of kitchen waste]
All (of) this has to go out into the rubbish bin.
We often use of after all in definite noun phrases (i.e. before the, possessives and demonstratives), but it is not obligatory:
All (of) the workers were given a pay-rise at the end of the year.
I gave all (of) my old books to my sister when she went to university.
What shall we do with all (of) this cardboard? Throw it out?