Ugh, horrible grainyness!

That's the major drasback to acrylics, they dry soooooooo fast. I keep a Q-Tip soaked in thinner in my airbrush stand and every time I set the brush down I wipe the tip off. The paint that is drying on the tip is causing most of your problems.

I normally use Tamiya acrylics as well and I normally thin them with alcohol. But I usually put a couple of drops of acrylic retarder in the paint to slow the drying time down. You can find it at any good art store under brand names like Createx, Golden, Liquitex (I think) and some others. It costs about $5 for a 6 or 8 oz bottle, and you only use a couple of drops at a time. Also, if you use Tamiya's thinner I think it has some retarder mixed in because it slows the drying time down significantly.

what type of airbrush do you have? here are my recommendations:

1. if you're using tamiya i recommend biting the bullet and purchasing tamiya thinner. alcohol as a thinner will tend to dry the paint both on the tip of your brush and in mid air as it travells to the subject. when it hits the subject, its about 70% dried.

2. keep a q-tip damp with the appropriate thinner and gently clean the tip of the needle occasionally.

3. for fine line work, thin even further that 50/50 and lower the pressure as low as you can get it and still apply the paint in a smooth coat.

i normally spray at max. 12 psi for anything except for primer and future. for fine line work such as camo demarcation lines, i'm get down under 10 psi where my guage quits reading properly. good luck friend. later.

You need a better gauge Salty , Mine reads all the way down.

i've gotten used to it jeff, i might screw something up if i buy a new one!!LOL. mine reads down to around 7psi which is low enough for me. later.

I'm using an Omni 4000G with an Iwata Quiet Air compressor.

Do you have a moisture trap? I don't think that's the problem, especially using acrylics, but they do help.

Your setup is similar to mine, I us a different compressor, but the airbrush and paint are the same. I spray at a little lower pressure though, normally 15 psi or less (frequently only around 8-10). Keep your tip wiped off and that will take care of a lot of the problem.

try spraying closer to the surface