Thanks to all for interesting answers
Annie, is the flatting agent a powder, as the baby talcum that Paul mention? I have planned to roll it on (outdoors among other boats), so the spray-only car paints will not work so well. I will go down to an old paint shop here and see what the keeper has got. Even if he doesn't have so much boat paints, he most probably can give advise on how make the paint matt, (flat?). Anyway, I am in no hurry - it is still a bit chilly here - I don't think we have seen +10 deg since October, but at least we are in for a nice, calm and sunny week (with almost frost at nights).
Arne