Learning to paint....

There are lots of variables that can affect the outcome of the topcoat/clear, ie temperature, humidity,speed of the reducer, capacity of compressor, not to mention how the gun is dialed in. It can be amazing how some little thing like temp an cause a lot of trouble!!
I love the SPI stuff but as their tech sheet notes, be aware you can have a delayed reaction with their epoxy primer and metal acid prep like OSPHO.