I detail vehicles as a side business and have for over 40 years. If you want to wax or polish (even with a buffer) and you want to make it easy on yourself, clay first--it's only been available outside of the commercial autobody stores for the past few years. Don't bother using the detailer that sometimes comes with the kit, just wash the vehicle and leave it wet--even soapy is OK, keep it wet and go over the body panels and even the glass with the clay. It will take off tar (tar remover works better, though) and overspray. Then spray off the vehicle, dry, and wax. BTW, if you ever get overspray on the plastic lenses of your glasses, it is about the only safe thing to use on them--and it works.
