As I spray, over the course of several hours, I just leave the finish in a lidded peanut butter jar on the work bench. It doesn't 'set' in the jar at the same rate it does when atomized from a gun. Overnight or longer, it goes in the fridge. I allow it to come up to room temperature, and then check the viscocity before I begin spraying again. If I have to add a splash of thinner to get it to the right consistency, I do.
The gun is cleaned, and ran, with cheap lacquer thinner between sessions. I don't leave finish in the gun.