Airtime AssassinG 10

Simply just run around during the normal course of game play as your going for orbs or vehicles and everytime you see a vehicle, any vehicle with the gang symbol above it (not the blue ones) those are police. If you really want you can even just grind this by jacking a vehicle (you don't have to drive it) if you're seen by another car of that gang they will jump out and start shooting you. Don't shoot back, or if you do you'll just have to wait/hide out until the gang symbol in the top right screen goes green. Then just rinse and repeat around every street there is always one or more if these cars. I was grinding these and it only took me about half an hour.