I have sprayed Lusterkote flat clear on Monokote for two models. I did NOT 'scuff' up the surface first as a lot of people suggest. It seems to be holding up very well after about a year and a half. It gives a satisfactory dull finish.

I don't fly these planes EVERY weekend, so maybe the flat might come off with a lot of use or with harsh cleaners, but it has been working pretty well for me.