You need a stripper!!
Poliprep will be a "butyl" solvent to remove wax etc.The greying is NOT due to trapped wax, since an acrylic coating will not stick if there is any wax underneath.What you are seeing is what happends to all acrylic clear coats eventually (how soon, depending upon amount sunlight, heat, amount of formulated UV blocker etc). That is what you see on car hoods after about 3 years.Best way to strip is using an ammonia based stripper (commercial) designed for acrylic floor coating removal. This is available at big stores like Home Depot.If you are going to redo the acrylic surface, then use the butyl cleaner and really well scuff. You can also use IG cleaners underneath an acrylic, although not directly recommended. You cannot use an acrylic over our sealants as they definitely will not stick- you would have to remove with a xylol-based wax remover.