i use Rustoleum Auto mobile primer i get it at wal mart. it works great with any type of paint you throw on it. It is thicker than your model brand primers and can leave behind a slight texture but nothing a little wet sanding with some fine grit wont cure and I always give it at least 24 hours to dry. Its dry to the touch in about 20 minutes and ok to go ahead and start wet sanding if you want.  Its cheap and readily available. Yes, the cure time on enamels can be pretty ridiculous. Generally i have found they take a week or two to fully cure. I used to use the testors enamel rattle cans and yes, I once waited about a month for that stuff to dry. but like i said before, if you can still smell the paint on the model, its more than likely still curing.

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over and out