Can immigrants do it themselves without looking for an intermediary?

Of course, one of the main reasons for finding an intermediary is that most people can't fill out many English forms, so they need to find an intermediary. In addition, the relevant preparation materials may not be clear, and you need to consult an intermediary. If you have no problem filling out the form and are well prepared, you basically don't need an intermediary, and most immigrants don't look for an intermediary.