This was sprayed over a spirit-based stain - https://www.bunnings.com.au/feast-wa...stain_p1569964
It was sprayed in fairly mild weather, so I don't think its a temperature problem.
I didn't feel that the coats were overly thick, but I have no reference point. I'm hoping its just that I don't have enough coats. I'm spraying another guitar with the same product, and will use more coats, so I'll have a comparison.

Sonic Mountain - when you say 'Application too Thick', that sounds like a separate issue to sufficient drying time. I believe I'm leaving it long enough to dry (3x light coats, 5 minutes apart, then leave it 3-5 days (weather dependent) before spraying the next triple-coat). In regards to 'application too thick', are you saying that if I sprayed a very heavy single coat, it will never cure fully?