Reducing Clear Coat

Was gonna paint the engine bay in my Dart. Mixed the stuff 4:1, just like instructions say. It was thick as pancake syrup. No way a spray gun would move it. Tried reducing it with urethane reducer and lacquer thinner.........both times it separated with a glob of stuff floating like a yolk in an egg. Tried upping pressure on my gun, but no way would it move that stuff. Please help!! I really need to get that engine bay finished.