Good that I tested this Mr Hobby flat "coat" (why not call it varnish?) on test piece of plastic - it melts paint. If I would try to use it on my actual model, it would not end well.

At the other hand, both Mig and AK spray can matte varnishes seems to work fine, former being a bit glossy, latter being more matte. Too bad I could only do short test with piece of plastic because whole day is windy as hell.