lyodbraun is correct about the clay bars. They "clean" the paint, not polish it. Which is what you need to do to get rid of swirl marks. And that's why plexus and turtle wax(crap) didn't help. They are cleaner/waxes that don't do a great job of either one. You need to get some actual polish or swirl remover. Some people call it rubbing compound.
Like with any detailing job, I recommend pinnacle, wolfgang, or menzerna but there are cheaper, easier to use alternatives that also do a pretty good job. If you have somewhere near you that sells 3M automotive stuff they have some good stuff or meguiars makes some good stuff also and you can probably find it in autozone, walmart, etc. Depending on the severity of the swirls, try some of their mirror glaze #9 or #205. The smaller number is for more severe swirl marks. They also have a product called "ultimate compound" that I haven't tried but I've heard good things about.
If you really want the swirl marks gone instead of just temporarily covering them up with colored wax it will take some time and patience. But you'll love the results when you're done. :thumbsup: