With the new patch this one's kinda a bad one to use. Before you could just use the old "run and gun" move and be able to get away without getting killed, now it's next to impossible. The sad thing is you only get $10,000 with every 5 kills. I'd say IF you really want to use it then what others have suggested by using "keep firing" is your best option. Once you get Invalid though I'd use that and "Fleet Foot" with this new patch. I use to use "Keep Firing" but you need to be able to move fast with this new patch or your dead for sure.
I got it the night before the update was released. I stopped trying to use it since all it takes for the other person to down me is two pistol shots and a fist while I'm there running around like a retard. If you try to use it by sitting behind cover and spraying whoever runs by, you probably won't get your 5 kills before the match ends.