A spider web should mean that you're either using too much PSI, too much thinner or are too close to the surface. I don't know what the ratio is for enamels: but find out what it is - you want it about like milk. Then try setting your PSI at about 18. Now start experimenting with distance and also any valve on your airbrush that will limit the amount of air/paint coming out. Set the thing where the paint barely comes out and then start from there: loosen the valve until you get a relatively thin spray. If you want to cover a lot of ground, open the valve all the way. I know not everyone agrees, but I would not push the pressure above 20 PSI - 25 max. If the pressure is that high, your paint is too thick.
One other thing. Look at the tip of your airbrush. If things start out okay and then it starts to sputter, you might have a tip that is partially clogging. (Should be a bigger problem with acrylics.) Keep a cheap paint brush in some enamel thinner and swab off the tip. Obviously if things are really clogged you've got to clean the brush.
This is not easy stuff but it's the single most important task to becoming a good modeler in my opinion. Don't get discouraged. If either of us got paid for every person who had trouble with airbrushing, we'd be rich enough to hire other people to build our kits.