As you all know, the "lomo" look and cross-processing E6 slide film in C-41 color negative chemistry has grown in popularity. I've been given, and also bought, some expired E6 film, mostly Ektachrome in 35mm and 4x5, and have been struggling to cross-process it. I know my C-41 chemicals (Rollei Digibase) are good, but most of the time all I get is an impenetrable, impossibly dark blue mask through which I can just barely discern an image. It's no good for scanning and I'd wager also no good for optical printing.
Are some films better than others for this treatment? Does the expiration have any bearing on this? Are there any ways to optimize my results, or should I just drop the whole idea entirely?