AdeB
Thanks guys, unfortunately XF-3 is one I'm still having issues with...I shall persevere.
Although I have actually found it seems to go on better over a matt back base...oh well.
Can you describe the issues you're having? Reading the previous posts, I can see that we all thought of the same thing, and that the issue you're having is getting a good, solid, bright yellow. That's the point of priming with white, it will make the overlaying yellow coat brighter (same goes for red, by the way). A dark primer will impart a dark shade to the overlaying color.
But we're assuming that's the problem. Since you mention Tamiya's XF-3 (which I also use), is it the color and how it looks when you're finished, or is the problem in applying it, it doesn't flow well through the airbrush for you, for example, or some other problem?
I have also used craft store acrylic (Americana), applied with an airbrush, and got a good color finish. There was a technical issue, in that craft store paints generally have coarser pigments than paints formulated for scale modelers to use, so there was some clumping, and when the paint dried and cured, it had a rougher surface, which I knocked down by rubbing with a piece of an old T-shirt.