The mattress method is useful for lo's who're really upset for being left alone. My ds is one of them, i just couldn't walk out of the room cause he'd freak and would be harder to console and the wakings would last hours.
Some lo's are just like that, they need the company and slooowly go back on track, be sure of that. It is really hard work but if you remain consistant with the timings and methods, be sure you'll succeed. For me, things got worse before they got better but there's hope, you just need to rest. Would your partner or a friend/relative would be willing to jump in the training? dh and i switched nights and although it was still tiring and hopeless we'd be ready for our night shift cause we had rested the night before.
Good luck and don't give up, it is so worth it!