Inconsistent finish when airbrushing

Hi All,

I'm new to airburshing and am encountering a problem which I wonder if someone could help with? Apologies if this issue has been tackled b" alt="" />efore but wasn't sure what to search for exactly. I'm currently building the Airfix 1:48 P-40b in RAF colours. I'm airburshing with an iwata revolution hp-cr and using Revell Acrylic paints. I've set the pressure to 20psi. I've thinned down the paint 50:50 using Revell's own paint thinner. I know Revell aren't the best paints but my choices are a bit limited where I live. 

The problem is that while I get good coverage and the paint flows fine, I don't seem to be able to get a consistent smooth finish. Looking at it straight on, the paint finish looks fine, but at certain angles you can see it is inconsistent. To better explain the problem I've attached a few photos. 

I've tried varying the pressure and making sure the paint is not too thick - I think the consistency is OK. I just don't seem to be able to resolve this. I'd apprecaite any hints or advice cause I am really not sure what to do.

Thanks

Ken