Varnish in Room 101

 After painting twenty thousand plus figures over the years I've tried everything at some point.

This is what I currently use through an airbrush, I don't thin or add anything. 
I use a cheap airbrush for varnishing.

Start with a first coat of (UK) Pledge Revive It (US/ROW use Klear). 

Next up Winsor & Newton Artists Gloss Varnish. UV protection and provides a clear and consistent surface for the matt varnish to adhere to. 

Now it's Winsor & Newton Artists Acrylic Matt Varnish, for some reason it dries more matt over enamel gloss varnish than acrylic gloss varnish.  One or two thin coats are usually sufficient.

Finally to get something so matt it could absorb light use AK Interactive Ultra-Matte Varnish.

Really shake it, then shake it again.