In regard to using the spray guns, I have ZERO experience with automotive finishes. But 20 plus years of cabinetry type finishes. In my experience it all comes down to fan pattern and flow rate. Both of those require practice. If you have anything to practice on try changing the spread of the "fan" and you flow rate (make sure your line and gun pressures are set accourding to your material needs) and your movement speed.
I am sure someone else here can chime in with line and gun pressures for your materials. Prctice and consistency are key. Keep at it and good luck.
