That's interesting, Charlie. Exactly that happened the last time I thinned a square bottle with lacquer thinner. My airbrush was shooting chunks. It seems like it also depends on color. I thinned Metallic Blue with lacquer thinner a few years ago, and it worked beautifully. The chunks came with Sublime. Also, lacquer thinner seems to turn MM semi-gloss black into flat. I've gone back to using Testors thinner, no issues there.
But you've completely destroyed its value as a collectible! Just kidding! It looks great. Having restored a few to "not pretty but fully functional" condition, l have a good idea how much work you put into it. That is some major rust removal. Did you replate the cap iron or just clean and polish it? Either way, nice job. Now go make some shavings!
You're doing nice work, Thomas. One thing: the spark plugs on a hemi are down inside the valve covers. In Andy's photo, you can see that there is just a rubber boot and the wire going into the valve cover.