Just a couple of questions, Is it humid there? If so, you might look into a moisture trap for the air brush. That will stop the water from spitting out when you are spraying.
And, are you using acrylics? There are thinners that go with the different brands, if you are thinning with tap water it can cause the paint to come out clumpy at times. Minerals in the water, I think, but one of our resident brains can probably give the correct answer. Anyways, the right thinner is the answer to blobs. Enamels are the same, use a thinner that is for airbrushing, it is more pure than the cheap brush cleaning stuff.
It's looking good, the preshading can still be seen, and there is something to be said for subtlety.