a regulator will fix this problem. You really can't fix this problem without one. Make sure the regulator comes with a water trap.
ie- you have a constant psi usually adjusted with a regulator...but since you don't have one..the only way to change the psi is to adjust the paint/thinning ratio...which is just foolish. Get a regulator.
Take a minute to think about it...no regulator = constant psi...that means, paints vary in viscosity , so , each paint will take a certain amount of thinner to atomize properly from your airbrush & look perfect. However..this constant psi will lead to hazy appearance because you now have paint that is being blasted out at a set psi , which is usually high, which leads to overspray, paint drying too fast will get you that appearance , you try to go over it again & it just adds more haze. The only way to beat this is too crank open the paint & soak everything. That in itself will lead to paint runs..loss of detail in your plastic by too much paint..so in other words,,GET A REGULATOR PRONTO! lol