You probably would not be able to get much correction out of any OTC orbit, they just simply won't spin fast enough to cut paint even with a good compound. You'd probably be adding more damage and RDS.
Save up and get either a PC i(if you do not plan on heavy correction and doing this for a living) or maybe a
Flex if you have the money. Then you can do some real correction and see some positive results.
Sorry to slightly get off topic and back to your question; you should strip the paint of any chemicals to see exactly what you are up against and also to help with the correction. The polish simply wouldn't polish if it is lubricated with wax would it? So basically, yes you have to strip it down to bare paint. Wash, clay, wash, and possibly an IPA wipedown (Isopropyl Alchohol) and then you should be ready to properly correct the paint.