Huh. Not familiar with that system so my experience is gonna be mostly worthless to ya.The Fuji semi-pro gravity sprayer has its own air compressor, with an adjustable air flow. 5 PSI:
https://www.fujispray.com/the-diy-series
5 psi is waaay too low to get a good pattern with a standard gun (even with a pressurized paint pot). Air flow that makes the pattern also dries the paint a bit on application. Airless is another totally different approach.
The basics still apply though... thick paint makes orange peel.
Try thinning it a bit, and try moving a lot faster to avoid runs. Also try varying your distance from the workpiece. This approach is actually more like using an airless, because of the high volume they produce.
Let us know how it goes.