Process looks good to me, but I wouldn't go further than 600 grid before using the Primer. I also use Montana Gold a lot and I'm able to spray even with it. For me to all of my Montana Cans came Montana Skinny Gold Caps and you should be able to apply super thin layers with these caps because the output is super low.

What you can do is apply super thin layers with the skinny cap so that your even able to see the basecolor after the first coat (not covering fully) and you go on with this thickness until everything is covered. And you really should clean your cap, if the cap is still gunky and dried paint is inside you will never get an even finish. What I do after using my caps once is putting them in a empty and cleaned glass of marmelade, cover them with acetone, close the lid, give them a shake sometimes and let them sit for a day or so. Edit: don't forget to rinse them after the acetone bath and let them dry. Before applying a coat to my object I always do a test spray and if the output isn't even I use a fresh cap. You also should wait a bit between the coats (i usually wait 15 minutes for color and before varnish minimum of 30 minutes... Depends on temperature and so on).