Several Airbrush Paint Questions

I'm completely new to the airbrush aspect of modeling so exscuse my ignorance on the paint subject but I can't find info I'd like to know.

1. When using a Pearl style paint do you get a better effect with a specific base type. Also what would the results generally be if sprayed directly over a white or gray primer?

2. Do paints such as Clear Blue, Clear Orange, ect. Give a colored tint when sprayed over a base color or what are they used for?

1. Most hobby paint pearls do look better over a base color. I use silver a lot.
White makes them a bit bright while I find grey makes them dull. Model Master pearls and metallics get darker the more coats you paint.
2. Your correct. Clear color or 'candies' are often sprayed over a silver or gold base if used simply as a color.

I get the feeling your talking about the HOK Kustum Kolor line...?
I know the had some instructions in the original big sets, but I have no idea if they have anything in the new sets.