I agree with most everything here except:
Lesbian porn where one chick gives the other chicks dildo/strapon cock a blowjob? Thats easy. She's lubing the cock. As in - "here suck this good, because I'm about to stick it all the way up you." It's an act of domination that has nothing to do with a blowjob simulation. Maybe I just have a twisted viewpoint. Anyway, enjoy.