Beat MoM first run. I had a little dude who shot brimstone with me. (Prayer Card + battery too) It took me a while to figure out you could control when he fired. :P
I didn't get any devil rooms after killing the main bosses. I got one from a Joker card and unlocked Lazarus. I came across an item called Magic Fingers. It took a coin to use, but I couldn't tell what effect it was having
I had to jack the gamma way up too.