Ed, that's exactly it – spray over the pigments with Dullcote.
This will temporarily emulsify the pigments before their color dries along with, and now into the flat finish coating on top.
You'll want just a thin layer of pigment coloring – anything that looks to the eye as being "porous", will capture the flat spray and the clear coat will fog.
If you don't like the look, or an area where the pigment might not be wanted, you can remove it with a moist brush, paper towel, etc.. After correcting your application, and once happy with where the pigments sit, then lock them in with a spray of Dullcote.
Btw, I always use a hair dryer to pre-heat my models before and after I apply a flat clear spray (I can spray outside in the winter too, by warming up my models or figs with a hair dryer).
paints 
