on AA for me the secret was to download that free dlc that had the infinite combat challenge map, get a few guys on the screen and then just attack leaping across the screen (L + square, R + square). throw in takedowns when you can and eventually a rhythm presents itself. you might have to counter sometimes or if you go too fast you might not have anything to hit, but you can always leap over someone to give yourself time. I think on 360 I got up to something like 130 before I lost it.
don't mean to imply that it's easy at all, but definitely doable.