This page is dedicated to common question in modelling. If you wanna find a topic in the mess below, use the search function! 
On Paint Thickness and mixing ratios:
If you want to prevent the paint from splattering/spluttering out you should thin it down more.
If your paint gets too thin and starts running all over the model you shld lower down the psi or mix in somemore paint to thicken it abit. lowering the psi helps alot with the overspray (particles flying everywhere). Test it on something before hitting your model with it. a psi of 10-15 is more than enough for thin paint. Dry it after every thin coat by using the AB to blow on it.
Another thing is the ratios are a rough guide, because sometimes paint doesn’t come in the exact thickness so-to-speak. It might have dried a little making it thicker than it should have been (esp. true for old paints or paints that the shop stored for very long). Try to make it to the consistency of milk… and remember to bubble it abit in the airbrush (if you are using an AB with the cup on top) by covering the nozzle, releasing the air and pulling back n the trigger.