I use hot glue, but some people use Silicone. Only reason I don't like to use silicone is because it takes too long to set.
Also, as far as the screen accuracy goes, I like screen accurate as much as the next guy, but a lot of screen accurate things aren't really ideal for trooping. Frown mesh helps prevent people from seeing your face. When I'm trooping that's all I'm really concerned about. If I had a nice set of armor that was always going to be on a mannequin, I'd keep it as screen accurate as possible including accurate fasteners etc, but that's not the case.