shooting single stage - question

[69Tom]

So I shot some UPOL high build primer this AM on my fenders and hood. As it's multi-purpose (high build, primer surfacer, and sealer) I used their 4:1:1 ratio to go for the primer surfacer. As I'm in Phoenix and I don't have a paint booth (great time of year to start painting, I know), I used ultra slow urethane reducer. While it isn't horrible, I was definitely getting some dry spray on it (I was using proper technique; was no more than 6-8" from the panel; kept trying to adjust the PSI at the gun). As it can easily be sanded and I did get some good coats down, I'm not super worried about it.

However, I am slightly concerned about shooting the paint (dry spray and orange peel). I'm using single-stage urethane from TPC global. I have slow reducer from them, but I'm definitely going to use the ultra slow urethan reducer I bought. They told me I should also use a 4:1:1 ratio. I'm definitely going to test it out on a junk hood I have before shooting it on the hours and hours I spend on my prepped panels, to work on PSI to use at the gun (24 psi with 1.4 tip recommended for my gun) and speed of passes.

I also wonder if I should reduce a bit more (not 4:1:2, but maybe 4:1:1.5 or so) as single stage can be a bit thick.

I wish I had normal temperatures or a paint booth, but I don't so I have to work with what I've got and shoot early morning, etc.

Thanks for any pointers from those experienced painters out there.