1) For the longest lasting results, all old products/oils/dirt need to be removed because our product needs a clean surface to bond to.
2) Using straight paint thinner or lacquer is very harmful to your plastics. That's why we recommend using our Super Cleaner as it was formulated to safely clean these surfaces.
But if you're going this route, using a mixture of isopropyl alcohol and water is the safest and best way.
Follow these steps:
(google ipa solution for detailing) Here is one article I've found: http://www.detailedimage.com/Ask-a-Pro/ask-a-pro-the-isopropyl-alcohol-ipa-wipedown/