Anything that will remove any oil or wax resudue on the surface to be painted. If you don't you, may get what is known as "fisheyes" in the paint which are small dots where the paint will not adhere properly to the surface. There was much discussion on what to use in a recent post. I use KAR-PREP SURFACE CLEANER by Kardol. In the past I have used mineral spirits without a problem. It would be wise to use something because if the paint gets "fisheyes" it all has to be sanded down and you start all over again.