If you've tried the Dream Coat and it didn't work, have you tried any other similar ones, like the Drybar liquid glass spray or anything?
I have heard so many good reviews about Dream Coat, but I found that it just seemed to coat each strand of hair separately in a way that meant that they were all wiry and wouldn't like smooth against each other (despite straightening). They really felt coated and it meant I had lots of volume but not in a nice way - just lots of individual strands, a bit straw like. I do have an awful lot of hair, though, and very frizzy/scraggly.
I've recently seen lots of recommendations for the Drybar Liquid glass sealant, which does something very similar. But all the reviews comparing it to the Dream Coat are from people who liked Dream Coat already and were trying to decide if Liquid Glass is as good as/better than. I've not read anything from people who didn't like Dream Coat.
I've also read some things from people who found that Dream Coat changed the texture of their hair, or made them start to lose/break hair - and they assumed it was why - but none of those people had also tried the Liquid Glass, so I don't know if it also has that effect on some people.