Ok, I give up. What did I do wrong?

I set out to prime my current project tonight and was using Mr. Surfacer 1200 for the first time. I mixed it 70% primer with 30% lac thinner.

When I sprayed it I got cobwebs! All over! Wierd.

And the airbrush (VL) had a hard time spraying it. I started at about 10psi. What to do?

All I could think of since the stuff didn't want to come out was to thin it some more. Up to about 50%. Pressure up to 12psi. This worked good but boy does it run empty quick.

So what I'm I doing wrong and was this the proper fix? Sure, it ended up working but I'm not sure I went about it the right way.

What say you?