I rushed back home eager to give it a bash with Vallejo's babies - having had a hit and miss affair with GW's Contrast Paints. The targets were a set of 10mm Pendraken Modern Warsaw Pact and NATO British ("Cold War Gone Hot" era) toys. The result was really a heavy all over green wash with blue-black boots and metal gun parts. They are relatively small kit so probably not the 25/28mm ideal target range, but to me it was still a "primer and very good wash" [all my crevesses are certainly covered] but still really wanting paint. Though probably "less" than normal. It certainly was a factory style productionline, which is good.
Afterwards I set off around the Internet to see what others thought. The accomplished painter "The Beard Bunker" was of interest.
My verdict: I think I am still missing the point and probably playing around with too small a scale for real benefit! Washes are probably good enough for 10mm.