I used an attack helicopter to get this (which you get at the end of Act 1). Pick up the chopper from Saint's HQ, and use the guns and missiles to get to 5 star gang notoriety. I did this against the Luchadores. You can go after other achievements, such as Haters Gonna Hate at the same time. If you don't already have it, you should also get Shake and Bake when you complete this.