When spraying metallics I generally spray 2 coats of base and once they're dry give it what's called a drop coat. Basically on the first 2 coats the flakes lie flat, so you turn down the pressure on the gun and allow a fine mist of metallic to come through. These stand on end and, once dried, can be lacquered to give you the desired finish.

Pretty impossible with rattle cans though mate. Post up some pics.