I've just inspected three of my son's planes 24 hours after I airbrushed themsprayed with Testors MM Acryl Flat Clear. They all have milky white patches on them.
I sprayed them with Future before and after applying the decals and 48hrs had passed since the last Future coat when I sprayed the flat..
I thinned the Flat clear 50/50 with Testors own acrylic thinner and have used it before with no ill effect.
Now that it's happened to me, after searching the web,it looks like I'm not the first modeller this has happened to.

Matt (SSGToms), I might try your suggestion of XF21 and future.

In the meantime does anyone have any suggestions for removing the milky blotches without damaging the rest of their handiwork .

White milky splotches sounds like moisture trapped in the finish. You can mist the areas with straight thinner to 'soften up' the finish and release the trapped moisture. It might take several attempts with a "light misting"(don't flood the piece with straight thinner)
Good luck....

Cheers,
Charles

I agree with Charles, white milky patches are either humidity or too thick application on a still wet coat.
Try shooting a light coat of Future on the areas, this should clear them up. Then reapply the flat coat.

The milky white areas are trapped moisture. As Mat said, a coat of Future will clear it up, then apply a coat of mat again, but wait for a not so humid day as that's where the moisture most likel y came from.

I really don't like the Model Master Acrylic Gloss or Mat clear coats. You're much better off using Testors Model Master Gloss coat and Dull coat. both are lacquer based, but dry quickly, and while they have a lacquer order, it's nothing like air brushing lacquer paint. and yes you need to thin it with Lacquer Thinner.