It wouldn't hurt, so if you don't mind the extra step I probably would do it. The two things both "clean" but they go about it differently. After claying and using the paint cleaner, you'll be ready to truly evaluate your paint and see where to go from there.
But if you're gonna use an abrasive polish anyhow, then I could also see skipping the paint cleaner. Not the *optimal* approach, but not a big deal either.