This thousands of Cerberus challenge is freaking hard ... i died so many times trying and still havent passed it. Theres too many ! im playing Normal mode
Reilly has provided the correct answer. If you completely ignore the first big dog until they stop spawning you should only ever have one or a very small handful of the big ones to deal with. Yes, eventually they do stop spawning.
Poseidon's rage is your best friend in this area. You want to kill them when they're still pups and Poseidon's rage will do just that. Also, I would recommend keeping your blades of chaos equipped and then using the spin move. I seem to have forgotten the name but you press L1 + Square. That part was a bitch on God mode.