SlickSand Featherfill requires a large tip. I use a large tip like they say to use. Not only does it get tge materials on , it goes on smoothly.
If you look ar guys like the Clown Bad Chad. He uses a gun with to small a tip, high pressure and thinned out. Gets a rough surface He then has to use lots of materials and half is wasted. He could spray half as much or less and get a better job. I also use the old style 3-M disposable cup liner system. Saves clean up. Now that patients ran out even Harbor Freight , Amazon and eBay has refills.
This is a good 2.5 tip https://www.amazon.com/dp/B09TMZJPKY?tag=fabo03-20
Still spray single stage, base and clear with my old Sharpe HVLP