Diluted PPG DX579 red scuff pad. You can also use it at only 50 50 diluted and leave wet rag in lomg time for deep pits just do not let dry out. Only use very hot water rinse as cold will flash rust.
Wipe with wipe down to remove contaminates just like anything else before priming with a,wax/grease like PPG DX 330 Acryli-clean wax and grease remover, or DuPont etc brand
My friend dues not use water but laqure thinner and shoots prime.
The directions say water, then wipe down, then prime
But he has never had a problem with just laqure thinner. I have done same as a test and no ill results