A solvent must be used to clean the entire paint area of wax, oil or other contaminants. Typically Prepsol, enamel reducer or other cleaners specific to this task are used.
Different solvents/cleaners are used dependent on the existing paint and what's going to be sprayed on.
'85 380 SL (sold)
'85 Carrera Flatnose
'71 280 SL Signal Red/Cognac