When teh paint is thick do you increase teh psi or decrease? Conversley if the paint is really thin low or high psi?

When the paint is too thick, all I do is just thin it out some more. If it's too thin, just lower the pressure in the airbrush.

well u should paint with between 20 to 23 pounds of air.
thats how much air i use

There are many different psi settings for different paint viscosities. Most settings can range anywhere from 15psi up to 30psi +/- . Your AB's needle or tip size will also dictate air pressure.
In most cases, you would be better off thinning the paint a bit and choosing a lower psi. A lower psi will help prevent paint - finish - problems such as "orange peel" ; when the paint dries before it has a chance to adhere to the model's surface.

Howdy godfather,

Kenc's post is dead on. Paint 'thickness' has almost nothing to do with AB pressure. All the airbrush is is a physical tool to apply a coating of paint. It has very little to do with the paint colour/consistency/or mixture.
To address the 'thickness' of the paint medium, finetune that before you pour it into the AB cup. :-)

...hth,

Tread.