Visually, you will notice specs of dirt, blemishes and dull areas. These are all indicators that it is time to deep clean your paint and apply one or more coats of wax. In general, there are two kinds of pre-wax cleaners. Polish also smoothes the paint surface, improving gloss. Used properly, a good polish will also remove swirl marks and other minor paint blemishes.
Most good polishes contain natural oils to moisturize the paint, which further adds to the gloss.
The second type of pre-wax cleaner is a true cleaner, not an abrasive. These products use citric acids to deep clean the paint and remove wax. Like a quality polish, pre-wax cleaners add oils to your paint to feed an enhance gloss. These products can be pricey due to the ingredients. If you have a convertible, after you wash is a good time to protect your canvas top.