Flashbangs are absolutely vital. Use them. After that, it's basically just trial and error. Figure out what works for you one painstaking step at a time. I haven't actually completed it, but I got to the final doors with 8 seconds to go and they just would not open for some reason. No idea why. 8 seconds is a balls-achingly long time when your mind is racing. I shouted, I cried, I banged my controller on the floor, I never tried again. I'd give yourself at least an hour to do it. It won't be over quickly.