Last night, I brushed on a layer of clear coat (flat, from Model Master) over a couple of pilot figures (they were already painted with a mix of flat and semi-gloss acrylic colors). Now I look at them and they are about as glossy as they can get! I’m not sure I understand they why of that. Either the bottle was mis-named flat when it is semi-gloss, or brushing is not the way to apply this. It may be that I didn’t mix the bottle’s contents well enough (although I thought I had stirred and mixed it well). But I am curious if anyone else has seen something like this.
I have been using Model Masters Acrylic clearflat for about two years to seal decals and weathering. I have never had a problem like you described. Like you said mabye it was mislabeled and really is glossy and not flat in the jar. I have never brushed it on though. I have found when airbrushing if you spray it straight from the bottle it will definetly lighten the colors of the model. If you thin it down this effect is not as noticeable. Brushing it on may lighten the colors considerably I would believe.
I have also been using MM flat clear for alot of years. It must have been labeled wrong or you didn’t apply enough of it. This product will dead flat anything you spray it on if that’s what you want.
I know this is an old thread, but I had the same problem. Turns out I didn’t mix the MM flat acrylic well enough. After doing some vigorous shaking, I got the desired flat effect.