I got to the consulate in Rio an hour before my appointment, there was a huge line of people waiting outside but I knew I didn't have to wait in the same line so I asked directions for a officer and they guided me to the right door. I went upstairs to the second floor, filled up a form, got my fingerprints scanned and then waited for my turn. The interviewee was very nice. She seemed very friendly and kind, she made just a couple questions. I made the oath and started the interview.
"Have you ever been married? "
" has he ever been married?"
"Do you have children?"
"Does he have children?"
"have you ever had a visa denied?"
Honestly I don't think someone needs to fear the interview as long as you have all the papers and you're telling the truth, you're all set.
Good luck everybody