There's "HG" printed before the colour-name, which means "High Gloss" ... so, what do you mean they aren't glossy? 
I'd like the ships to look as close to original Playmobil as possible, so I guess I would better use "mat" or "silk gloss" paints...
Ah, ok it was not clear in the pic, I thought it was ''HQ'' which I had no idea what it is....
This gloss argument reminds me of the ''shiny'' or ''not too shiny'' playmobil gold golour argument
These sprays are geeral purpose sprays so they do fine for any surface. I've never used a ''silk gloss'' paint so I cant help you there. But from general painting I know that, one, any colour you paint over another is taking over the first colour, and two, if you colour lightly you might get a lesser shade of the original colour. So your idea might work, meanig just spray a thin layer over the first colour.
