Looking for tips on using Scalecoat 2 paint

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So, I've been working on some F&C milk cars as mentioned in another thread under this "Tips and Tricks" part of the forum. I've gotten one done to the point where I've applied a few coats of Scalecoat 2 Pullman Green (twice ) The issue I am having is the paint is going on grainy (in some places). So, I'm looking for some advice on what might be causing the paint to do that and some tips to correct it. Let me set up how I was applying the paint. I mixed the paint 60/40, 60 Scalecoat thinner/40 paint, in that range, more to the 60% side. Reefer was primed with Tamiya Fine Scale primer. Air brush set about 20-25 psi. My paint booth is now in the garage, my first attempt to paint the reefer was during the week and it was not as humid as it was over the weekend here in NJ. When I painted it during the week, I did multiple coats over a 4 day period. Toward the end of laying on the coats I noticed the graininess. I stripped the paint on Saturday, washed in mild soap and air dried, primed again, tested application on a styrene sheet and found it to be smooth, then applied a few coats to the reefer every 3 to 4 hours. Found more graininess, but not as bad as it was the first time. The bottom of the reefer was the way I would expect to see Scalecoat to look, the sides not so much. Top of the reefer seems OK, too, this time. This is the first time I am using Scalecoat 2 paint, I've used Scalecoat 1 on other projects and not had this problem.

Some thoughts or observations I think happened are: 1. the paint was drying as it was being applied, because I was holding the airbrush to far away from the reefer in some spots? And if this is the case, how far away should the air brush be from project being painted. 2. Bad mix with thinner to paint ratio? 3. Humidity? 4. PSI is off. 5. Should I try and paint the reefer in one setting instead of multiple coats?

And I was wondering if, after decals are applied, would a coat of flat sealer remove the graininess and even everything out?

Here are some pictures of what is going on:









Thx,

Mark (Ugh)