Solo, #20 on top of a carnauba is a bad idea. Sealant's won't bond to a surface with oils or waxes on it. The sealant needs to go first and then the carnaubas.
I seem to remember some discussion some time ago about #20 possibly having some cleaning properties. Am I imagining that conversation, or is that true? It seems to me that every liquid product I've used from Meguiar's smells pretty strongly of solvents.