John Nicholson is a custom painter who uses Tru-Color Paint for his business. John uses Rust-oleum Professional Grade Lacquer Thinner from their Auto Paint product line to thin the paint for spraying multiple light coats. He uses a mix of 55/45% paint to thinner and then a hair dryer is used to help set/dry the paint. I would still recommend storing Tru-Color Paint with Tru-Color's own thinner as the soft plastic bottles do loose media (thinner) over time.
John also uses Model Master Primer for models made of brass metal and then uses Tru-Color Paint over that base. He uses a mix of 80% primer to 20% distilled water. I would expect Tru-Color's own Primers (both dark and light) to get the same results.
For this car John used Tru-Color's Southern Pacific Lark Light Gray and Lark Dark Gray. He uses a good-old Paasche Model H airbrush. Iwata need not apply. The model H is easy to work with and clean. Air pressure is set at 25 PSI. When a brass model is completely painted he will place the model in the oven with a setting of 150 degrees and leave it in there for about half an hour.