I managed to salvage about a pint of the Valspar Low Gloss paint from the open can. Still have not received the hardener but decided to to a HVLP pass on the back of one of the fenders anyway. Hardener is not necessary...just speeds things up. Thinned it 8:1 with lacquer thinner. Laid down nicely. Not really sure what to reduce it with. Mineral spirits cut it as well. I scotch guarded the fender rather than sanding it so all of the orange peel from the primer shows through. I'll sand the next one to better reflect what I intend to do on the exterior. I'm pretty happy with the low gloss sheen.
Note the heavy orange peel.
Couldn't pass up this all original '75 Schwinn Junior Stingray distraction....Only requires some fresh tires, surface rust removal and a cleanup so no appreciable slow down on the truck.