Kim,
Did the Alsa paints come with detailed application instructions? Some metallics require larger tips, higher air pressures, greater distance, etc. Speed and amount of reducer can vary with temp. too.
For example, I have sprayed the Alsa ghost chrome and it's high air pressure combined with low fluid and slow buildup.
If you haven't given them a call I would do so. They might be able to help trouble shoot your light dark streaks.
Cheers,
John
p.s. and yes, I remember those special spray guns for heavy metal flake that stir the paint constantly. A couple of glass marbles can be used along with "shaking" (more like a circular rolling motion) to keep the metallics in even suspension. You don't want to put the gun down for a length of time and let things settle out and start spraying without "shaking" things up. You also need to stir the paint can before refilling the gun to keep all applications consistent.