Start picking 16th notes at a reasonable speed, perhaps 120 bpm. You can slow down the tempo if that's too fast. Keep increasing the tempo until you are satifsied with your speed.

As with all techniques, this requires a reasonable amount of practicing.
just make just each pick stroke is clean and sounds good, because if you can get a great technique going a slower tempo's then it will be much easier when you start hitting the fast stuff......well thats how i started anyway