I’ve tried a number of flat or matt finishes over the years; acrylic, oil based and lacquer based.  While all produced a nice flat finish Dullcote was the only brand that produced a surface that I could use a white pencil on for adding chalk marks the rest the pencil didn’t have enough of a rough surface for the white lead to adhere to. 
--
Charlie Duckworth 
Omaha, Ne.

Long story, but my elders told me that DullCoat was simply clear lacquer with talc added to get the extremely flat finish it is known for.  This talc has two side effects, 1) it lightens the finish already applied to the model, and 2) it has some "tooth" to it allowing chalks, etc. to adhere to it.  Don't know if this is true, but that's what I was told.

-- John

John
I was told the same thing about talc being added. 
--
Charlie Duckworth 
Omaha, Ne.

I heard it was French chalk 

I've used the Hataka flat; it's very flat and I've used white pencils on it successfully.

Craig Zeni
Cary NC