Dusk balls actually only net you a 3.5x boost according to this person: http://dragonflycave.com/capture.aspxQuick Ball should work well since you should never be in a battle with them for very long and Dusk Ball gets the same 4x capture rate if it's at night. Fast Balls get a 3x capture rate since Entei and Raikou run away.
Fast Balls also operate based on your target's base speed, not whether or not they flee. Either way, for the first five turns, use Quick Balls, after which switch to Dusk Balls, and if you're really unfortunate, switch to Timer Balls after thirty turns.