I cannot remember the title or the author of this fic. I think it was a season 4 or 5 fic. I remember Sam and Cas were talking about Dean in the beginning, and Dean being bi (and I think closeted) came up. If I remember correctly Cas tried to offer to let Dean use him to experiment, and Dean thought Cas was the one coming out to HIM, so they ended up thinking they were helping each other. Any help finding this fic would be greatly appreciated! ^_^