I can't tell you anything about Coppola, but I had 2 Brazilian Blowouts with very different results -- one not so great.
First one was fabulous! The stylist really knew what he was doing. I have fine, shoulder length hair and he spent a good 45 minutes applying the product in very thin layers of hair with very, very little product. He actually explained to me that many stylists use too much. He uses only a small capful for most clients and used even less on me. There were no fumes at all during this treatment. He also spent just as much time blowdrying and hot ironing my hair. It was so smooth it was like dolls hair. I had horrible frizzed/heat damanged ends before the treatment, and after, you would have never known.
2nd treatment, about 3.5 months later, I had done by a different stylist. Got a great deal with a Groupon (I guess you get what you pay for
). She used genuine BB products (well at least they smelled the same and were in the same bottles). She totally globbed on the product in about 10 minutes. So much that when she was blowdrying my hair I was choking on the fumes, just from the blowdryer! Also the blowdryer so was hot it was buring my scalp. She didn't spend the time drying it super smooth and straight, and she also whipped the hot iron through in thick sections. It was straight and flat, but not anything like it was with my first treatment. Ends were frizzy and it hung totally limp on my head. Very different results. That's actually what drove me to start going curly again and trying the curly girl method.
I just think too much product, too much heat, etc. can damage your hair or just go overall bad. I think there is a fine line between done right for perfect results, or a rushed job with imperfect results. Were your treatments done by the same person?