Thanks Snake, Nick, Don, Joe, Tom, Dave, Carl, Lee, Marty, Mark, and Christopher.
I use McDonald's coffee stirs - they have a flat end - to measure the amount of Pearl-Ex powder to use. About 2 stirs 1/4 full does it for me. So into a medicine pill cup and mix with HOK SG100 about 2/3 full. That gives me almost a full cup in the airbrush. Final color greatly depends on the base color. I use Duplicolor primer in either black, dark grey, light gray, or white. I have spoon tests for all the varieties I've mentioned.