Oils over Model Master Dullcote?

Neither.  The thinner for oil paints will eat into the enamel paints and the lacquer dullcoat.  You can try using an acrylic clear coat like Model Master Acryl flat or glossy.  There can be a problem with this.  If you don't get perfect coverage of the acrylic coat, the thinner from the oil paints will cause lifting in that area.  This will happen especially since the surface gets floaded with thinner.  I would recommend not doing the dot method on your current model and the next model use acryic paints instead.  Just my opinion.

-Jesse

Thank you for saving my model, Jesse!  Looks like I'll have to invest in some acrylic paints then.  Oh well....if it helps pull our economy out of the tank, I'll do my part.

Eric

No problem.  I use enamels myself.  I don't use the dot method.  I don't really care for it.  I think it makes a vehicle look too weathered and unrealistic.  I prefer to use pastels as I think the dust looks more realistic (for armor that is).  It's up to you.

-Jesse