Howdy Gaz,
Dullcote is a "matte" finish made by Testors. It dries really fast (although the smell is pretty strong until dry...usually in about 15 min.). It will take the shine off of anything and not leave a sticky or "tacky" finish on your model, in fact, it leaves the model feeling some what like it was coated with baby powder to me.
However.....Do not use Dullcote on clear polystyrene like canopys or windows, it will cause them to "cloud up".
It can be purchased at most places that sell models and paint for models for about $4 (US).
Testors also makes a "Glosscote" which adds a deep shine to models, although to me, it has abit more of a "sticky" or "tacky" feeling to it until completely dry (it usually dries thoroughly in a few hours and it also has a strong smell until dry).
Below are pics of both products:
I hope this helps, Have a good day,
Greg aka GW