I would suggest going with a medium gray sealer, then use another regular metallic, THEN do the Orion.
Orion is VERY transparent, so you basically want it in a Silver before you coat it with Orion.
You can get away without doing this on motorcycle parts, but to do a quite a bit of Orion to do complete car. You'll probably find it quicker, easier, and you'll use less materials in the long run.
:luck: