It all depends on which product you use. Some require longer to "cure" than others. Zaino polishes take between 6 to 24 hrs to cure without the use of their new additive called ZFX which significantly reduces the curing time (it does work by the way). Other products like Blackfire and Klasse require little to no time between coats. All of these polishes can be layered without the yellowing, streaking or hazing associated with multiple coats of a cheap wax. And the collective effect of the additional coats really does improve the shine. As for using a spray in between applications, I have found this is useful only because it helps remove any excess polish left over after buffing. Therefore it actually increases the shine and reflective qualities of the finish. I know Sal has other reasons for using his Z6 in between applications but I think he will admit this is one of the major reasons. Anyway I hope this answers your questions.
