The problem indeed is a too quick drying of the paint. Actually you're throwing pieces of paint on the model that stick, but do not have the opportunity to flow into eachother, making a neat coat. This results in the orange peel.
One way to sort this out is too make your paint some thinner, or the suggested pressure-tinkering.
An other, which I used to make a smoke-coat on a S-3 Viking canopy, is to first spray the orange pee paint, but directly afterwards spray the subject with a coat of pure thinner (which you have to anyway to clean you airbrush). The orange peel coat probably hasn't hardned out yet, so the thinner will then make a fluent coat. Be sure not to use too much thinner, as it will make the paint drip and run over your model. So be delicate!
Take a peek on my website, under built models, S-3 Viking for the smoked canopy.