There are epoxy primers for automotive uses, but most base coats are waterborne, and the important part of automotive finishes is the clear coat, which is there to protect the base coat from UV damage. Most clear coats are acrylic melamine. Even they need the extra protection of wax to stay in top shape.

The biggest problem I see with using carnauba wax is that after you decide it doesn't work you'll have an incredibly difficult time trying to get all of it off well enough for a new finish to stick to it 100%. My guess is that you won't know that you didn't get it all off until your new finish doesn't stick and is covered with fisheyes, or it starts to delaminate days, weeks, or months after you finish it.

If you want to take out a few steps from the normal building process, you can add graphite powder to your fill coats of epoxy, then fair and sand up to 600 and even buff it if you want.

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