We need a wet palette (you can find instructions everywhere on the net - I use the Citadel grass tuft box, some paper towels and a sheet of baking parchment) and some very special, but thankfully easily available and cheap brushes. These brushes are flat eye shadow (yes, not artistic or hobby, but MAKEUP brushes!). These are syntetics, with very thickly places thin bristles, which are overall fairly rigid, but their tips are very smooth and nice to the touch, almost fluffy. This is what makes them ideal - I bought mine in a Hebe or Rossman drugstore, you can buy these anywhere you buy makeup stuff, just ask for eye shadow blending brushes. They should be very cheap, I bought these for an equivalent of $2.
You need to take a minimal amount, just a drop, of paint out of the cup and place it on the wet palette. Then smear it around so it stays on the bristles and doesn't leak (make sure there's not too much of paint or water, it should NOT flow). Afterwards do a heavy drybrush ("overbrush") of the areas that are supposed to be basecoloured with this paint. Use two thin layers (cheers, Duncan!) if required, Retributor Gold over black primer was a very pale gold on the first layer, only after second it shone properly. Just make sure the paint doesn't gather in recesses and by the detail, smear it around and try to use "mashing" motion, too. The brush is made for that and this makes the pigment placement a lot smoother.
This technique works with all the paint that is a bastard to base with - yellows, red, etc.