Hello!
I don't know the products you intend to use, but even if they are "airbrush ready" it's good to thin them a little - with the right stuff. Especially when it's hot.
As for the pressure it also depends a little on the temperature, but just experiment a little and you will know. If you get spitting or "big drops" raise the pressure a little and/or add some thinner. If the paint lands dry and dusty on the painted surface, add some thinner and lower the pressure. You have too much thinner in the paint if you have problems getting the coverage of the color... Sometimes, when the paint is thin "spiders" start to form - in that case try moving the airbrush further away from the painted surface, don't open the needle so much and move the airbrush faster (don't point it at one spot for too long) before lowering the amount of thinner in the mix.
Hope this helps - good luck and have a nice day
Paweł