I think it's worth noting the weather and atmosphere. Right now in the UK, East Midlands it's humid. We've had a cool start to the day with lots of rain. now at 5pm temperatures have increased and the humidity here has rocketed. Unless you had access to a spray booth with a ventilation or atmosphere system you'd very likely have problems where I am today. Spraying outdoors or in a poorly insulated outbuilding with a window open you do run the risk of milky varnish (matt or gloss) on a day with even medium to low humidity. The same problem can occur in winter with cold humid weather.
When the weather is like this I use a paint on acrylic varnish. Using a nice flat brush you won't get brush marks, especially if you use a good brand of varnish like Vallejo.
Other factors to consider with spray varnish and clouding/milkiness is to give plenty of time between coats, if the first coat hasn't cured you can get a milky second.
Hairdryers or drying ovens can be used to clear clouding and milkiness but it's never guaranteed
Often you see people exclaim that "VarnishABC" or "GlossCote123" never gives them problems but it's more likely that those folk happen to live in the perfect weather environment for spray varnishing...
