It would depend on your spray gun more than anything. I use a cheap Harbor Freight HVLP detail spray gun at about 20psi. You can find identical ones on EBay for $12- $15. I have an old Badger detail spray gun I tried and at 20psi it would only dribble and spit out the paint. It's an older non HVLP type and likes 40+psi.
The instruction sheet should have starting settings. My DeVilbiss is 23 psi but also important is the flow and fan controls. Too much paint, splatters. Too little may take forever to coat. Too wide a fan wastes paint, too narrow may go on too thick.
If you describe the results, someone may be able to advise on adjustments.
Grainy, I would increase pressure first then if still grainy, reduce the paint flow a tiny bit.
Also, it helps a lot to have a really good regulator at the gun for consistency.
Microair is awesome. Never moves so pressure stays exactly where it's set.
I use the cheap HF gun for shooting Azko. I have the version with the pressure gauge on the gun. I think this is very helpful if you don't have it there I would suggest you add one.
The pressure that is important is the pressure once you pull the trigger. This end up being pretty low even with a relatively high pressure beforehand. I think mine is somewhere around 40PSI. Again the number that I look at is the pulled trigger PSI which ends up being between 5 and 10 PSI. I tune it by testing my pattern real quickly before each session.
The other thing that I have been doing is adding a very small amount of lacquer thinner to the mix. Also make sure you pour the paint through a filter as you pour it into the cup.
I just shot a batch over the weekend and it turned out great. I hate waiting the 30 minutes once its mixed by otherwise its works out great.
