Hello and welcome to just answer. I highly recommend using the McGuire's wax remover if you can get it from your auto parts store. Their products are as close to being professional quality but still available at the consumer level. If you cannot get the McGuire's products, then Turtle Wax would be your next choice. It works very well also.
Then apply the new polish, and you should have a nice finish. Just be sure to follow the directions on the containers.
Thank you. XXXXX polish and then wax or wax first and then polish?