This is what I'm using and it works for me. Add this into a text file, save it as a .bat, put it in the directory where you have your miner and run it.
@echo off
start phoenix -u http://username:password@pit.deepbit.net:8332/ -k poclbm DEVICE=0 VECTORS BFI_INT FASTLOOP=false AGGRESSION=11 WORKSIZE=128
start phoenix -u http://username:password@pit.deepbit.net:8332/ -k poclbm DEVICE=1 VECTORS BFI_INT FASTLOOP=false AGGRESSION=11 WORKSIZE=128