You know what the first thing I'm going to say is, don't you? 
Thin your paint. Unthinned, even if you cranked it up to 40PSI, the best you could hope for is a few splutters and then nothing. It's a recipe for instant "tip dry" too - paint leaving the nozzle will dry almost instantaneously on the needle/nozzle tip, causing a blockage.,
Use Tamiya X-20A thinner, Isopropyl alcohol or denatured alcohol, but thin your paint. Don't use water or Windex though.
Start around 1:1 paint to thinner and adjust if necessary. Don't be afraid to use more thinner as in my experience, it's very difficult to over-thin Tamiya acrylics. I've gone 4:1 thinner to paint and beyond with a Badger 200. You will start to find the limits of Tamiya's thinner at about 3:1 thinner to paint. Go much past that and it starts to behave like water, beading and running.
You will find that you get a much smoother and cleaner finish when you thin your paint, but you will need to experiment a little to find exatly how much thinning you need, depending on what you're trying to achieve. Base coats, one to two parts thinner to one part paint should do the trick. For more detailed work, thinner paint and less air.
Good luck. :-)
PS: I'm sure that someone will suggest using Tamiya Lacquer thinner too, but I would suggest leaving this for the moment and concentrate on getting the basic technique down first. Tamiya lacquer thinner will work and can be advantageous in some situations, but you don't need to go there just yet.